Abstract: The rotational stiffness of the zero-stiffness flexible hinge is approximately zero, which overcomes the defect that ordinary flexible hinges require driving torque, and can be applied to flexible grippers and other fields. Taking the inner and outer ring flexible hinges under the action of pure torque as the positive stiffness subsystem, the research Negative stiffness mechanism and matching positive and negative stiffness can construct zero stiffness flexible hinge. Propose a negative stiffness rotation mechanism——Crank spring mechanism, modeled and analyzed its negative stiffness characteristics; by matching positive and negative stiffness, analyzed the influence of structural parameters of crank spring mechanism on zero stiffness quality; proposed a linear spring with customizable stiffness and size——Diamond-shaped leaf spring string, the stiffness model was established and the finite element simulation verification was carried out; finally, the design, processing and testing of a compact zero-stiffness flexible hinge sample were completed. The test results showed that: under the action of pure torque,±18°In the range of rotation angles, the rotational stiffness of the zero-stiffness flexible hinge is 93% lower than that of the inner and outer ring flexible hinges on average. The constructed zero-stiffness flexible hinge has a compact structure and high-quality zero-stiffness; the proposed negative-stiffness rotation mechanism and the linear The spring has great reference value for the study of flexible mechanism.

0 Preface

Flexible hinge (bearing)

^[1-2]

Relying on the elastic deformation of the flexible unit to transmit or convert motion, force and energy, it has been widely used in precision positioning and other fields. Compared with traditional rigid bearings, there is a restoring moment when the flexible hinge rotates. Therefore, the drive unit needs to provide output torque to drive and Keep the rotation of the flexible hinge. Zero stiffness flexible hinge

^[3]

(Zero stiffness flexural pivot, ZSFP) is a flexible rotary joint whose rotational stiffness is approximately zero. This type of flexible hinge can stay at any position within the stroke range, also known as static balance flexible hinge

^[4]

, are mostly used in fields such as flexible grippers.

Based on the modular design concept of the flexible mechanism, the entire zero-stiffness flexible hinge system can be divided into two subsystems of positive and negative stiffness, and the zero-stiffness system can be realized through the matching of positive and negative stiffness

^[5]

. Among them, the positive stiffness subsystem is usually a large-stroke flexible hinge, such as a cross-reed flexible hinge

^[6-7]

, generalized three-cross reed flexible hinge

^[8-9]

and inner and outer ring flexible hinges

^[10-11]

etc. At present, the research on flexible hinges has achieved a lot of results, therefore, the key to design zero-stiffness flexible hinges is to match suitable negative stiffness modules for flexible hinges[3].

Inner and outer ring flexible hinges (Inner and outer ring flexural pivots, IORFP) have excellent characteristics in terms of stiffness, precision and temperature drift. The matching negative stiffness module provides the construction method of the zero-stiffness flexible hinge, and finally, completes the design, sample processing and testing of the zero-stiffness flexible hinge.

1 crank spring mechanism

1.1 Definition of negative stiffness

The general definition of stiffness K is the rate of change between the load F borne by the elastic element and the corresponding deformation dx

K= dF/dx (1)

When the load increment of the elastic element is opposite to the sign of the corresponding deformation increment, it is negative stiffness. Physically, the negative stiffness corresponds to the static instability of the elastic element

^[12]

.Negative stiffness mechanisms play an important role in the field of flexible static balance. Usually, negative stiffness mechanisms have the following characteristics.

(1) The mechanism reserves a certain amount of energy or undergoes a certain deformation.

(2) The mechanism is in a critical instability state.

(3) When the mechanism is slightly disturbed and leaves the equilibrium position, it can release a larger force, which is in the same direction as the movement.

1.2 Construction principle of zero-stiffness flexible hinge

The zero-stiffness flexible hinge can be constructed by using positive and negative stiffness matching, and the principle is shown in Figure 2.

(1) Under the action of pure torque, the inner and outer ring flexible hinges have an approximately linear torque-rotation angle relationship, as shown in Figure 2a. Especially, when the intersection point is located at 12.73% of the reed length, the torque-rotation angle relationship is linear

^[11]

, at this time, the restoring moment Mpivot (clockwise direction) of the flexible hinge is related to the bearing rotation angleθ(counterclockwise) the relationship is

Mpivot=(8EI/L)θ (2)

In the formula, E is the elastic modulus of the material, L is the length of the reed, and I is the moment of inertia of the section.

(2) According to the rotational stiffness model of the inner and outer ring flexible hinges, the negative stiffness rotating mechanism is matched, and its negative stiffness characteristics are shown in Figure 2b.

(3) In view of the instability of the negative stiffness mechanism

^[12]

, the stiffness of the zero-stiffness flexible hinge should be approximately zero and greater than zero, as shown in Figure 2c.

1.3 Definition of crank spring mechanism

According to literature [4], a zero-stiffness flexible hinge can be constructed by introducing a pre-deformed spring between the moving rigid body and the fixed rigid body of the flexible hinge. For the inner and outer ring flexible hinge shown in FIG. 1, a spring is introduced between the inner ring and the outer ring, I .e., a spring-crank mechanisms (SCM) is introduced. Referring to the crank slider mechanism shown in Figure 3, the related parameters of the crank spring mechanism are shown in Figure 4. The crank-spring mechanism is composed of a crank and a spring (set stiffness as k). the initial angle is the included angle between the crank AB and the base AC when the spring is not deformed. R represents the crank length, l represents the base length, and defines the crank length ratio as the ratio of r to l, I .e. = r/l (0<<1).

The construction of the crank-spring mechanism requires the determination of 4 parameters: the base length l, the crank length ratio , the initial angle and the spring stiffness K.

The deformation of the crank spring mechanism under force is shown in Figure 5a, at the moment M

_γ

Under the action, the crank moves from the initial position AB

_Beta

turn to AB

_γ

, during the rotation process, the included angle of the crank relative to the horizontal position

_γ

called the crank angle.

Qualitative analysis shows that the crank rotates from AB (initial position, M & gamma; Zero) to AB0 (“dead point”location, M

_γ

is zero), the crank-spring mechanism has a deformation with negative stiffness characteristics.

1.4 The relationship between torque and rotation angle of crank spring mechanism

In Fig. 5, the torque M & gamma; clockwise is positive, the crank angle & gamma; counterclockwise is positive, and the moment load M is modeled and analyzed below.

_γ

with crank angle

_γ

The relationship between the modeling process is dimensioned.

As shown in Figure 5b, the torque balance equation for crank AB & gamma is listed.

In the formula, F & gamma; is the spring restoring force, d & gamma; is F & gamma; to point A. Assume that the displacement-load relation of the spring is

In the formula, K is the spring stiffness (not necessarily a constant value),δ

xγ

is the amount of spring deformation (shortened to positive),δ

xγ

=|B

_Beta

C| – |B

_γ

C|.

Simultaneous type (3)(5), moment M

_γ

with corner

_γ

The relationship is

1.5 Analysis of the negative stiffness characteristics of the crank-spring mechanism

In order to facilitate the analysis of the negative stiffness characteristics of the crank-spring mechanism (moment M

_γ

with corner

_γ

relationship), it may be assumed that the spring has a linear positive stiffness, then formula (4) can be rewritten as

In the formula, Kconst is a constant greater than zero. After the size of the flexible hinge is determined, the length l of the base is also determined. Therefore, assuming that l is a constant, formula (6) can be rewritten as

where Kconstl2 is a constant greater than zero, and the moment coefficient m & gamma; has a dimension of one. The negative stiffness characteristics of the crank-spring mechanism can be obtained by analyzing the relationship between the torque coefficient m & gamma; and the rotation angle & gamma.

From equation (9), Figure 6 shows the initial angle =π relationship between m & gamma; and crank length ratio and rotation angle & gamma;, & isin;[0.1, 0.9],& gamma;& isin;[0, π]. Figure 7 shows the relationship between m & gamma; and rotation angle & gamma; for = 0.2 and different . Figure 8 shows =π When, under different , the relationship between m & gamma; and angle & gamma.

According to the definition of crank spring mechanism (section 1.3) and formula (9), when k and l are constant, m & gamma; Only related to angle & gamma;, crank length ratio and crank initial angle .

(1) If and only if & gamma; is equal to 0 orπ or ,m & gamma; is equal to zero; & gamma; & isin;[0, ],m & gamma; is greater than zero; & gamma; & isin;[,π],m & gamma; less than zero. & isin;[0, ],m & gamma; is greater than zero; & gamma;& isin;[,π],m & gamma; less than zero.

(2) & gamma; When [0, ], the rotation angle & gamma; increases, m & gamma; increases from zero to the inflection point angle & gamma;0 takes the maximum value m & gamma;max, and then gradually decreases.

(3) The negative stiffness characteristic range of the crank spring mechanism: & gamma;& isin;[0, & gamma;0], at this time & gamma; increases (counterclockwise), and the torque M & gamma; increases (clockwise). The inflection point angle & gamma;0 is the maximum rotation angle of the negative stiffness characteristic of the crank-spring mechanism and & gamma;0 & isin;[0, ];m & gamma;max is the maximum negative moment coefficient. Given and , the derivation of equation (9) yields & gamma;0

(4) the larger the initial angle , & gamma; the larger 0, m

_γmax

bigger.

(5) the larger the length ratio , & gamma; the smaller 0, m

_γmax

bigger.

In particular, =πThe negative stiffness characteristics of the crank spring mechanism are the best (the negative stiffness angle range is large, and the torque that can be provided is large). =πAt the same time, under different conditions, the maximum rotation angle & gamma of the negative stiffness characteristic of the crank spring mechanism; 0 and the maximum negative torque coefficient m & gamma; Max is listed in table 1.

2 Construction of zero-stiffness flexible hinge

The matching of positive and negative stiffness of the 2.1 is shown in Figure 9, n(n 2) groups of parallel crank spring mechanisms are evenly distributed around the circumference, forming a negative stiffness mechanism matched with the inner and outer ring flexible hinges.

Using the inner and outer ring flexible hinges as the positive stiffness subsystem, construct a zero-stiffness flexible hinge. In order to achieve zero stiffness, match the positive and negative stiffness

simultaneous (2), (3), (6), (11), and & gamma;=θ, the load F & gamma of the spring can be obtained; and displacementδThe relationship of x & gamma; is

According to section 1.5, the negative stiffness angle range of the crank spring mechanism: & gamma;& isin;[0, & gamma;0] and & gamma;0 & isin;[0, ], the stroke of the zero stiffness flexible hinge shall be less than & gamma;0, I .e. the spring is always in a deformed state (δxγ≠0). The rotation range of the inner and outer ring flexible hinges is±0.35 rad(±20°), simplify the trigonometric functions sin & gamma; and cos & gamma; as follows

After simplification, the load-displacement relationship of the spring

2.2 Error analysis of positive and negative stiffness matching model

Evaluate the error caused by the simplified treatment of equation (13). According to the actual processing parameters of zero stiffness flexible hinge (Section 4.2):n = 3,l = 40mm, =π, = 0.2,E = 73 GPa; The dimensions of the inner and outer ring flexible hinge reed L = 46mm,T = 0.3mm,W = 9.4mm; The comparison formulas (12) and (14) simplify the load displacement relationship and relative error of the front and rear springs as shown in Figures 10a and 10b respectively.

As shown in Figure 10, & gamma; is less than 0.35 rad (20°), the relative error caused by the simplified treatment to the load-displacement curve does not exceed 2.0%, and the formula

The simplified treatment of (13) can be used to construct zero-stiffness flexible hinges.

2.3 Stiffness characteristics of the spring

Assuming the stiffness of the spring is K, the simultaneous (3), (6), (14)

According to the actual processing parameters of zero stiffness flexible hinge (Section 4.2), the change curve of spring stiffness K with angle & gamma; is shown in Figure 11. In particular, when & gamma;= 0, K takes the minimum value.

For the convenience of design and processing, the spring adopts a linear positive stiffness spring, and the stiffness is Kconst. In the whole stroke, if the total stiffness of the zero stiffness flexible hinge is greater than or equal to zero, Kconst should take the minimum value of K

Equation (16) is the stiffness value of the linear positive stiffness spring when constructing the zero stiffness flexible hinge. 2.4 Analysis of zero-stiffness quality The load-displacement relationship of the constructed zero-stiffness flexible hinge is

Simultaneous formula (2), (8), (16) can be obtained

In order to evaluate the quality of zero stiffness, the reduction range of flexible hinge stiffness before and after adding the negative stiffness module is defined as the zero stiffness quality coefficientη

η The closer to 100%, the higher the quality of zero stiffness. Figure 12 is 1-η Relationship with crank length ratio and initial angle η It is independent of the number n of parallel crank-spring mechanisms and the length l of the base, but only related to the crank length ratio , the rotation angle & gamma; and the initial angle .

(1) The initial angle increases and the zero stiffness quality improves.

(2) The length ratio increases and the zero stiffness quality decreases.

(3) Angle & gamma; increases, zero stiffness quality decreases.

In order to improve the zero stiffness quality of the zero stiffness flexible hinge, the initial angle should take a larger value; the crank length ratio should be as small as possible. At the same time, according to the analysis results in Section 1.5, if is too small, the ability of the crank-spring mechanism to provide negative stiffness will be weak. In order to improve the zero stiffness quality of the zero stiffness flexible hinge, the initial angle =π, crank length ratio = 0.2, that is, the actual processing parameters of section 4.2 zero stiffness flexible hinge.

According to the actual processing parameters of the zero-stiffness flexible hinge (Section 4.2), the torque-angle relationship between the inner and outer ring flexible hinges and the zero-stiffness flexible hinge is shown in Figure 13; the decrease in stiffness is the zero-stiffness quality coefficientηThe relationship with the corner & gamma; is shown in Figure 14. By Figure 14: In 0.35 rad (20°) rotation range, the stiffness of the zero-stiffness flexible hinge is reduced by an average of 97%; 0.26 rad(15°) corners, it is reduced by 95%.

3 Design of linear positive stiffness spring

The construction of zero stiffness flexible hinge is usually after the size and stiffness of the flexible hinge are determined, and then the stiffness of the spring in the crank spring mechanism is reversed, so the stiffness and size requirements of the spring are relatively strict. In addition, the initial angle =π, from Figure 5a, during the rotation of the zero-stiffness flexible hinge, the spring is always in a compressed state, that is“Compression spring”.

The stiffness and size of traditional compression springs are difficult to customize precisely, and a guide mechanism is often required in applications. Therefore, a spring whose stiffness and size can be customized is proposed——Diamond-shaped leaf spring string. The diamond-shaped leaf spring string (Figure 15) is composed of multiple diamond-shaped leaf springs connected in series. It has the characteristics of free structural design and high degree of customization. Its processing technology is consistent with that of flexible hinges, and both are processed by precision wire cutting.

3.1 Load-displacement model of diamond-shaped leaf spring string

Due to the symmetry of the rhombic leaf spring, only one leaf spring needs to be subjected to stress analysis, as shown in Figure 16. α is the angle between the reed and the horizontal, the length, width and thickness of the reed are Ld, Wd, Td respectively, f is the dimensionally unified load on the rhombus leaf spring,δy is the deformation of rhombic leaf spring in the y direction, force fy and moment m are equivalent loads on the end of a single reed, fv and fw are component forces of fy in the wov coordinate system.

According to the beam deformation theory of AWTAR[13], the dimensionally unified load-displacement relation of single reed

Due to the constraint relationship of the rigid body on the reed, the end angle of the reed before and after deformation is zero, that isθ = 0. Simultaneous (20)(22)

Equation (23) is the load-displacement dimensional unification model of rhombic leaf spring. n2 rhombic leaf springs are connected in series, and its load-displacement model is

From formula (24), whenαWhen d is small, the stiffness of the diamond-shaped leaf spring string is approximately linear under typical dimensions and typical loads.

3.2 Finite element simulation verification of the model

The finite element simulation verification of the load-displacement model of the diamond-shaped leaf spring is carried out. Using ANSYS Mechanical APDL 15.0, the simulation parameters are shown in Table 2, and a pressure of 8 N is applied to the diamond-shaped leaf spring.

The comparison between the model results and the simulation results of the rhombus leaf spring load-displacement relationship is shown in Fig. 17 (dimensionalization). For four rhombus leaf springs with different inclination angles, the relative error between the model and the finite element simulation results does not exceed 1.5%. The validity and accuracy of the model (24) has been verified.

4 Design and test of zero-stiffness flexible hinge

4.1 Parameter design of zero-stiffness flexible hinge

To design a zero-stiffness flexible hinge, the design parameters of the flexible hinge should be determined according to the service conditions first, and then the relevant parameters of the crank spring mechanism should be calculated inversely.

4.1.1 Flexible hinge parameters

The intersection point of the inner and outer ring flexible hinges is located at 12.73% of the reed length, and its parameters are shown in Table 3. Substituting into equation (2), the torque-rotation angle relationship of the inner and outer ring flexible hinges is

4.1.2 Negative stiffness mechanism parameters

As shown in fig. 18, taking the number n of crank spring mechanisms in parallel as 3, the length l = 40 mm is determined by the size of the flexible hinge. according to the conclusion of section 2.4, the initial angle =π, crank length ratio = 0.2. According to equation (16), the stiffness of the spring (I .e. diamond leaf spring string) is Kconst = 558.81 N/m (26)

4.1.3 Diamond leaf spring string parameters

by l = 40mm, =π, = 0.2, the original length of the spring is 48mm, and the maximum deformation (& gamma;= 0) is 16mm. Due to structural limitations, it is difficult for a single rhombus leaf spring to produce such a large deformation. Using four rhombus leaf springs in series (n2 = 4), the stiffness of a single rhombus leaf spring is

Kd=4Kconst=2235.2 N/m (27)

According to the size of the negative stiffness mechanism (Figure 18), given the reed length, width and reed inclination angle of the diamond-shaped leaf spring, the reed can be deduced from formula (23) and the stiffness formula (27) of the diamond-shaped leaf spring Thickness. The structural parameters of rhombus leaf springs are listed in Table 4.

surface4

In summary, the parameters of the zero-stiffness flexible hinge based on the crank spring mechanism have all been determined, as shown in Table 3 and Table 4.

4.2 Design and processing of the zero-stiffness flexible hinge sample Refer to literature [8] for the processing and testing method of the flexible hinge. The zero-stiffness flexible hinge is composed of a negative stiffness mechanism and an inner and outer ring flexible hinge in parallel. The structural design is shown in Figure 19.

Both the inner and outer ring flexible hinges and diamond-shaped leaf spring strings are processed by precision wire-cutting machine tools. The inner and outer ring flexible hinges are processed and assembled in layers. Figure 20 is the physical picture of three sets of diamond-shaped leaf spring strings, and Figure 21 is the assembled zero-stiffness The physical picture of the flexible hinge sample.

4.3 The rotational stiffness test platform of the zero-stiffness flexible hinge Referring to the rotational stiffness test method in [8], the rotational stiffness test platform of the zero-stiffness flexible hinge is built, as shown in Figure 22.

4.4 Experimental data processing and error analysis

The rotational stiffness of the inner and outer ring flexible hinges and zero-stiffness flexible hinges was tested on the test platform, and the test results are shown in Figure 23. Calculate and draw the zero-stiffness quality curve of the zero-stiffness flexible hinge according to formula (19), as shown in Fig. 24.

The test results show that the rotational stiffness of the zero-stiffness flexible hinge is close to zero. Compared with the inner and outer ring flexible hinges, the zero-stiffness flexible hinge±0.31 rad(18°) stiffness was reduced by an average of 93%; 0.26 rad (15°), the stiffness is reduced by 90%.

As shown in Figures 23 and 24, there is still a certain gap between the test results of the zero stiffness quality and the theoretical model results (the relative error is less than 15%), and the main reasons for the error are as follows.

(1) The model error caused by the simplification of trigonometric functions.

(2) Friction. There is friction between the diamond leaf spring string and the mounting shaft.

(3) Processing error. There are errors in the actual size of the reed, etc.

(4) Assembly error. The gap between the installation hole of the diamond-shaped leaf spring string and the shaft, the installation gap of the test platform device, etc.

4.5 Performance comparison with a typical zero-stiffness flexible hinge In literature [4], a zero-stiffness flexible hinge ZSFP_CAFP was constructed using a cross-axis flexural pivot (CAFP), as shown in Figure 25.

Comparison of the zero-stiffness flexible hinge ZSFP_IORFP (Fig. 21) and ZSFP_CAFP (Fig. 25) constructed using the inner and outer ring flexible hinges

(1) ZSFP_IORFP, the structure is more compact.

(2) The corner range of ZSFP_IORFP is small. The corner range is limited by the corner range of the flexible hinge itself; the corner range of ZSFP_CAFP80°, ZSFP_IORFP corner range40°.

(3) ±18°In the range of corners, ZSFP_IORFP has higher quality of zero stiffness. The average stiffness of ZSFP_CAFP is reduced by 87%, and the average stiffness of ZSFP_IORFP is reduced by 93%.

5 Conclusion

Taking the flexible hinge of the inner and outer rings under pure torque as the positive stiffness subsystem, the following work has been done in order to construct a zero-stiffness flexible hinge.

(1) Propose a negative stiffness rotation mechanism——For the crank spring mechanism, a model (Formula (6)) was established to analyze the influence of structural parameters on its negative stiffness characteristics, and the range of its negative stiffness characteristics was given (Table 1).

(2) By matching the positive and negative stiffnesses, the stiffness characteristics of the spring in the crank spring mechanism (Equation (16)) are obtained, and the model (Equation (19)) is established to analyze the effect of the structural parameters of the crank spring mechanism on the zero stiffness quality of the zero stiffness flexible hinge Influence, theoretically, within the available stroke of the flexible hinge of the inner and outer rings (±20°), the average reduction in stiffness can reach 97%.

(3) Propose a customizable stiffness“spring”——A diamond-shaped leaf spring string was established to establish its stiffness model (Equation (23)) and verified by finite element method.

(4) Completed the design, processing and testing of a compact zero-stiffness flexible hinge sample. The test results show that: under the action of pure torque, the36°In the range of rotation angles, compared with the inner and outer ring flexible hinges, the stiffness of the zero-stiffness flexible hinge is reduced by 93% on average.

The constructed zero-stiffness flexible hinge is only under the action of pure torque, which can realize“zero stiffness”, without considering the case of bearing complex loading conditions. Therefore, the construction of zero-stiffness flexible hinges under complex load conditions is the focus of further research. In addition, reducing the friction that exists during the movement of zero-stiffness flexible hinges is an important optimization direction for zero-stiffness flexible hinges.

references

[1] HOWELL L L. Compliant Mechanisms[M]. New York: John Wiley&Sons, Inc, 2001.

[2] Yu Jingjun, Pei Xu, Bi Shusheng, etc. Research progress on design methods of flexible hinge mechanism[J]. Chinese Journal of Mechanical Engineering, 2010, 46(13):2-13. Y u jin champion, PEI X U, BIS call, ETA up. State-of-arts of Design Method for Flexure Mechanisms[J]. Journal of Mechanical Engineering, 2010, 46(13):2-13.

[3] MORSCH F M, Herder J L. Design of a Generic Zero Stiffness Compliant Joint[C]// ASME International Design Engineering Conferences. 2010:427-435.

[4] MERRIAM E G, Howell L L. Non-dimensional approach for static balancing of rotational flexures[J]. Mechanism & Machine Theory, 2015, 84(84):90-98.

[5] HOETMER K, Woo G, Kim C, et al. Negative Stiffness Building Blocks for Statically Balanced Compliant Mechanisms: Design and Testing[J]. Journal of Mechanisms & Robotics, 2010, 2(4):041007.

[6] JENSEN B D, Howell L L. The modeling of cross-axis flexural pivots[J]. Mechanism and machine theory, 2002, 37(5):461-476.

[7] WITTRICK W H. The properties of crossed flexure pivots and the influence of the point at which the strips cross[J]. The Aeronautical Quarterly, 1951, II: 272-292.

[8] l IU l, BIS, yang Q, ETA. Design and experiment of generalized triple-cross-spring flexure pivots applied to the ultra-precision instruments[J]. Review of Scientific Instruments, 2014, 85(10): 105102.

[9] Yang Qizi, Liu Lang, Bi Shusheng, etc. Research on rotational stiffness characteristics of generalized three-cross reed flexible hinge[J]. Chinese Journal of Mechanical Engineering, 2015, 51(13): 189-195.

yang Q I word, l IU Lang, BIS voice, ETA. Rotational Stiffness Characterization of Generalized Triple-cross-spring Flexure Pivots[J]. Journal of Mechanical Engineering, 2015, 51(13):189-195.

[10] l IU l, Zhao H, BIS, ETA. Research of Performance Comparison of Topology Structure of Cross-Spring Flexural Pivots[C]// ASME 2014 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, August 17–20, 2014, Buffalo, New York, USA. ASME, 2014 : V05AT08A025.

[11] l IU l, BIS, yang Q. Stiffness characteristics of inner–outer ring flexure pivots applied to the ultra-precision instruments[J]. ARCHIVE Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science 1989-1996 (vols 203-210), 2017:095440621772172.

[12] SANCHEZ J A G. Criteria for the Static Balancing of Compliant Mechanisms[C]// ASME 2010 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, August 15–18, 2010, Montreal, Quebec, Canada. ASME, 2010:465-473.

[13] AWTAR S, Sen S. A generalized constraint model for two-dimensional beam flexures: Nonlinear strain energy formulation[J]. Journal of Mechanical Design, 2010, 132: 81009.

About the author: Bi Shusheng (corresponding author), male, born in 1966, doctor, professor, doctoral supervisor. His main research direction is fully flexible mechanism and bionic robot.

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After the above introduction, I mainly understand what are the concepts of electromechanical hardware. In the article, what is hardware and what is electromechanical, I gave you an introduction. If we want to buy, we can first look at its concept. Then you can know whether you need this kind of thing, if you need it, you can buy it, and, in the article, you also know what the classification of electromechanical hardware is.

Hardware electromechanical classification of hardware electromechanical

Hardware tools, hardware accessories, construction hardware, daily hardware, locks and abrasives, kitchen and bathroom hardware, furniture hardware, hardware materials, welding materials for welding machines, electrical appliances, wires and cables, lighting appliances, instruments and meters, security equipment and supplies , mechanical and electrical equipment, mechanical equipment and hardware materials. Refers to the general term for various metal devices made of iron, steel, aluminum and other metals through forging, rolling, cutting and other physical processing. It has a wide range and many products. It is divided into 12 categories according to the use and material category.

Hardware tools include various manual, electric, pneumatic, cutting tools, auto maintenance tools, agricultural tools, lifting tools, measuring tools, machine tools, cutting tools, fixtures, knives, molds, cutting tools, grinding wheels, drills, polishing machines, Tool accessories, measuring tools, abrasives, etc. Hardware and electromechanical products need to constantly adapt to changes in market development laws. At present, many products are highly competitive. Taking molds as an example, the domestic market share of low-end molds exceeds 99%. However, market price competition is serious and profit margins are extremely low. High-end molds The profit is high but 80% depends on imports. But many companies have realized this and started to carry out technological updates and product innovation research and development. In the future, the hardware and electrical industry will gradually move towards the era of technological competition rather than price competition.

At present, the hardware and electrical industry transactions are mostly concentrated in the wholesale markets of big cities. Taking Chengdu as an example, there are several hardware and electrical markets in the area of Jinfu Road, such as Wanguan, Jinfu, West, and Steel City. Billion business district. However, this kind of physical market wholesale is more and more infiltrated by the Internet. At present, many large websites are starting to set up online markets for the hardware and electrical industry. Although the wholesale of the physical market is still the mainstream, but in terms of hardware and electrical products companies still wholesale The market is following the Internet, and the future development will form a situation where online and offline interactive stations are half the sky. The offline market has a tendency to shift to small and medium-sized cities.

Hardware electrical appliances refer to electrical appliances made of gold, silver, copper, iron, aluminum, tin and other metal materials.

The most common hardware appliances include power supplies, electrical lamps, electrical sockets, electrical switches, electrical connectors, metal components such as resistors, capacitors, reactors, etc.

Hardware: traditional hardware products, also known as "hardware". It refers to five metals: gold, silver, copper, iron, and tin. After manual processing, it can be made into knives, swords and other works of art or metal devices. Hardware in modern society is more extensive , such as hardware tools, hardware parts, daily hardware, construction hardware and security supplies, etc. Most of the small hardware products are not final consumer goods.

Extended information:

Process performance:

Refers to those properties of the material's ability to withstand various processing and handling.

Casting performance: Refers to some technological properties of whether the metal or alloy is suitable for casting, mainly including flow performance, ability to fill the mold; shrinkage, the ability to shrink the volume of the casting when it solidifies; segregation refers to the inhomogeneity of the chemical composition.

Welding performance: refers to the characteristics that two or more metal materials are welded together by heating or heating and pressure welding, and the interface can meet the purpose of use.

Top gas section performance: refers to the performance of metal materials that can withstand upsetting without breaking.

Cold bending performance: refers to the ability of metal materials to withstand bending without breaking at room temperature. The degree of bending is generally expressed by the ratio of bending angle (outer angle) or bending center diameter d to material thickness a, the larger a is or the smaller d/a is , the better the cold bending property of the material.

Stamping performance: the ability of metal materials to withstand stamping deformation without cracking. Stamping at room temperature is called cold stamping. The inspection method is tested by cupping test.

Forging performance: the ability of metal materials to withstand plastic deformation without breaking during forging.

What is hardware, electromechanical, construction hardware, hardware materials, industrial hardware

Hardware electromechanical is a general term, including hardware furniture, electric tools and other hardware-related production materials and products within its scope. Hardware refers to gold, silver, copper, iron, tin, and generally refers to metal. Today's hardware is commonly used as metal Or the collective name of products such as copper and iron. Electromechanical is mechanical electronics, which refers to a class of products related to machinery and electricity.

Architectural hardware started from handicraft workshops such as blacksmith shops, coppersmith shops, and tinsmith shops. China had nail-making workshops in the Tang Dynasty, and nails, door bolts, locks, door knockers, etc. were made by hand. However, because ancient buildings mostly use wood And stone structure, architectural hardware has developed slowly in the past thousands of years. After the 19th century, with the widespread use of metal materials and the needs of social life, architectural hardware has developed rapidly, and many production steel nails, hinges, Small factories or workshops for bolts, window hooks, faucet valve parts, wire woven window screens, etc. Later, mechanical processing equipment was gradually used instead of handmade, forming many specialized enterprises. With the continuous improvement of various building facilities standards Improvement, modern architectural hardware products have developed from a single variety to serialization, and the requirements for their aesthetics and decorative effects are getting higher and higher. The production technology of architectural hardware products has also made great progress. Most of the products have been changed from the original semi-manual , Semi-mechanical operation has developed into semi-automatic or fully automatic mechanical assembly line production. The materials used in architectural hardware have been expanded from traditional copper alloys and low-carbon steels to zinc alloys, aluminum alloys, stainless steel, plastics, glass steel and various composite materials. .

There are many kinds of architectural hardware. Generally, they can be divided into five categories: door and window hardware, plumbing hardware, decoration hardware, silk nail mesh hardware products and kitchen equipment.

Door and window hardware is a general term for various metal and non-metal fittings installed on the doors and windows of buildings. According to the purpose, it is divided into building door locks, handles, braces, hinges, door closers, handles, bolts, window hooks, anti-theft chains, Induction door opening and closing device, etc.

Plumbing hardware is a general term for the hardware used in building water supply and drainage systems, heating systems and toilets. It usually includes faucets, showers, falling water, toilet accessories, toilet accessories, spray massage bathtub accessories, valves, pipe connections and toilets. other hardware.

Decorative hardware is a general term for decorative ornaments and products used inside and outside buildings. They often have both use and protection functions. There are mainly combined metal ceilings, lightweight flexible partitions, and metal decorative panels.

Wire nail mesh hardware products are mostly made of carbon steel or non-ferrous metals. It is a general term for various wire, nails, nets and mesh products. It is widely used in construction projects such as buildings.

The wire is cold-drawn and rolled from carbon steel or non-ferrous metal, and has various thickness specifications. It is mainly divided into galvanized iron wire, stainless steel wire and special metal wire. Galvanized iron wire: also known as galvanized low-carbon steel wire, is cold-drawn The surface of the steel wire is coated with a zinc layer. It is widely used in rowing, fence, shed repair, weaving net, weaving sieve, hoop and barbed wire, flood control, construction, bridge repair and well drilling construction projects and telegraph Overhead communication lines such as telephones, cable broadcasting, etc. Two strands of galvanized iron wire twisted with each other and galvanized barbed wire with thorns (Figure 1), are specially used to erect defensive facilities around military restricted areas or important factories and warehouses. Stainless steel wire: excellent mechanical properties, high temperature resistance, good corrosion resistance, widely used for weaving various wires, used in various instruments, household appliances, medical and sanitary appliances, chemical and food machinery. Special metal wire: common Products include steel core wire, nickel-plated steel wire, Dumet wire, round copper wire, etc., which are widely used in the electric light source industry. Construction hardware

Nails are punched from low-carbon steel wires or copper and aluminum wires. They are used to connect wood and other fiber products. Nails are composed of three parts: nail head, nail shank and nail tip. There are 3 types of nails for shoes and special nails. Nails for construction: products include round steel nails, felt nails, saddle nails, corrugated nails, corrugated screws and flat-headed round copper nails, etc. (Figure 2). It can be used to nail wooden boxes, furniture, wooden bridges, agricultural tools, etc. Nails for shoemaking: the products include ordinary shoe nails (autumn leather nails), sesame nails, fishtail nails, round steel nails for leather shoes, etc., mainly used for nailing Cloth shoes, leather shoes, etc. are also increasingly used in buildings. Special nails: products include round steel nails for splicing, cement steel nails and tire grinding nails, etc. Construction hardware

The net is woven from metal wire or non-metal wire, or punched from metal sheet. It mainly includes window screen, expanded metal mesh and hot-dip galvanized wire mesh. Window screen: a silk fabric woven with metal wire or non-metal wire .Installed on general indoor doors and windows, food cabinet doors and food container covers to prevent the invasion of flies, mosquitoes and other flying insects. The metal wires used for window screens are generally low-carbon steel wires, aluminum wires, magnesium wires, copper wires and stainless steel wires , the non-metallic wires used include plastic, paper thread, hemp thread, etc. The surface of the metal wire window screen is painted with green paint, galvanized or slush-molded; some non-metal wire window screens are dyed, and some are in natural color. Metal sheet with mesh. There are expanded metal mesh and expanded aluminum mesh. The expanded mesh is made of low carbon steel annealed sheet or cold-rolled sheet. The mesh is diamond-shaped. According to the length of the mesh surface, it is divided into large mesh and small mesh. Large mesh The surface of the mesh is coated with iron red anti-rust paint, which is generally used as a protective cover on the machine, or used as a protective layer on glass greenhouses and windows, or used as an isolation ventilation wall in factories, warehouses, substations and other places. Without paint, it is generally used on the walls, pillars, ceilings, etc. of buildings, so that cement and lime are not easy to fall off, and it plays the role of steel bars. The thick steel mesh can also play a load-bearing and anti-skid role, and is mostly used as a dock , ships, machine room aisle and escalator pedals. Aluminum expanded metal mesh is punched with thin aluminum plate, the mesh is diamond-shaped or herringbone, and the surface is electro-dyed into various colors. It has the characteristics of light weight, beautiful appearance and durability. The main Used in instruments, meters, household appliances, and industrial machinery and equipment for ventilation, protection, filtration, and decoration. Hot-dip galvanized wire mesh: It is formed by weaving high-quality galvanized iron wire. It has certain anti-corrosion and oxidation resistance. According to the weaving The grid shape can be divided into square mesh and hexagonal mesh, etc. It is widely used in various places that need to be enclosed, and the large square mesh woven mesh is also widely used in cement hulls.

Kitchen equipment Equipment and machinery for kitchen operations. It mainly includes washing tables, operating tables, vegetable cutters, stoves, stoves, ovens, kitchen cabinets, storage and range hoods. Some of them are used as fixed supporting appliances for the kitchen. It is built together with the house and delivered for use; the other part is configured by the house user according to the needs (see daily hardware).

Hardware common sense: what are the floor drains?

The floor drain is an important interface connecting the drainage pipe system and the indoor floor. As an important part of the drainage system in the house, its performance directly affects the quality of the indoor air, and it is very important for the odor control in the bathroom. The floor drain is a must for home decoration Where are the few places, what are the floor drains? The following editor will introduce them one by one.

Hardware common sense: what are the floor drains?

What are the floor drains? According to the deodorant method, the floor drains are mainly divided into three types: water deodorant floor drains, sealed deodorant floor drains and three-proof floor drains.

The anti-odor floor drain is our most traditional and common. It mainly uses the tightness of water to prevent the emission of peculiar smell. In the structure of the floor drain, the water storage bay is the key. Such a floor drain should try to choose a deep water storage bay. You can't just look at the beautiful appearance. According to the relevant standards, the body of the new floor drain should ensure that the water seal height is 5cm, and have a certain ability to keep the water seal from drying up to prevent odor.

Now there are some ultra-thin floor drains on the market, which are very beautiful, but the anti-odor effect is not very obvious. If your bathroom space is not a bright room, then it is best to choose some traditional ones. Sealed anti-odor floor drains refer to adding a The upper cover seals the floor drain body to prevent odor. The advantage of this floor drain is that it looks modern and avant-garde, but the disadvantage is that you have to bend down to lift the cover every time when you use it, which is troublesome.

But recently, an improved sealed floor drain has appeared on the market. There is a spring under the upper cover. When using the upper cover with your foot, the upper cover will pop up, and you can step back when not in use. It is relatively more convenient. Three defenses The floor drain is the most advanced anti-odor floor drain so far. It installs a small floating ball at the lower end of the floor drain body, and uses the water pressure and air pressure in the sewer pipe to withstand the ball so that it is completely closed with the floor drain, thereby Play the role of deodorization, insect repellent and anti-overflow.

What hardware appliances include

Hardware home appliances mainly refer to electrical appliances made of metal, including hardware, daily hardware, construction hardware, hardware parts, security supplies, etc., among which hardware refers to nails, screws, locks, springs, etc., daily hardware has Scissors, embroidery needles, architectural hardware including door bolts, door locks, anti-theft chains, stoves, etc.

What are the varieties of hardware appliances

Hardware home appliances refer to electrical appliances made of gold, silver, aluminum, tin, copper, iron and other metals. They are mainly divided into two categories, including power supplies, lamps, sockets, switches, capacitors, reactors, resistors, etc. .

Hardware home appliances are divided into two types: hardware and electrical appliances. Among them, hardware is also called hardware, which refers to hardware products in the traditional sense, such as metal knives, swords and maintenance tools.

The range of hardware appliances in modern society is more extensive, mainly divided into hardware tools, hardware parts, daily hardware, construction hardware, security supplies, etc., among which daily hardware refers to products such as pans, bowls, needles, scissors, and architectural hardware refers to door locks. , door bolts and other metal accessories.