Value Of Applied Load Research Articles

Prediction of Wrinkling Initiation and Growth in Aluminum 5456-H116, Alloy Sheets by Finite Element Analysis of Yoshida Test

Wrinkling is one of the most undesirable effects during forming of thin sheet metal plates. It deforms the surfaces and either hampers further assembly or creates stress concentration regions which may fail during operations. Yoshida wrinkling test is considered as one good tool to analyse the wrinkling properties of sheet metals. Alluminium alloys are most commonly used in aviation industry where wrinkling initiation and its propagation is considered an even serious defect. Present research was therefore focussed on Finite Element simulations of Allumium Alloy-5456-H116 metal sheets specimens of the standard shape of Yoshida specimen. During simulations the applied load values were equal to Yield strength, yield strength +10%, and Yield strength -10%. Wrinkling initiation and propagation was observed as deformations along X,Y and Z axis on a predefined path of the specimen and stress values at this path were also evaluated. Findings have been established through an overview of deformation along each axis corresponding to stress values at that location on the path.

Friction and wear performance of polyamide 6 and graphite and wax polyamide 6 composites under dry sliding conditions

The friction and wear performance of pure polyamide-6 (PA-6), 5wt%, 15wt% graphite filled polyamide-6 and 4wt% wax filled polyamide-6 (PA-6+4% wax) sliding against stainless steel under dry sliding conditions were studied using a pin-on-disc tribometer. The influences of filler type, content, applied load and sliding speed on tribological properties were investigated. Tests were carried out at sliding speeds of 0.4, 0.8, and 1.6m/s and applied load values of 50, 75 and 100N. Scanning electron microscopy (SEM) was utilised to examine worn surfaces microstructure and wear mechanisms. The results showed that, the friction coefficient for PA6 and PA6 composites increases with the increasing load and sliding speed values while wax filled composite showed insensitivity to the change in load values. In addition, it was observed that their wear rate is highly influenced by sliding speed and insignificantly influenced by the change in applied load values. For the range of materials in this investigation, the lowest wear rate is 6.910−15m2/N for 4wt% wax filled PA-6 composite and the highest rate is 2.12×10−14m2/N for pure polyamide-6. The wear mechanism includes transferred film and involves deformation and adhesive wear processes.

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In this investigation the friction and wear performance of GUR 1020 medical grade ultra-high molecular weight polyethylene (UHMWPE) polymer under dry sliding, distilled water and egg albumen lubrication conditions were evaluated. The sliding experiments were carried out on a pin-on-disc tribometer. The contact configuration used was a polymer pin on a rotating AISI 304L stainless steel disc. Wear tests were carried out for 30 min duration at room temperature with 50, 100 and 150 N applied load values and at 0.50, 1.0 and 2.0 m/s sliding speeds condition. The results show that the coefficient of friction for GUR 1020 medical grade UHMWPE polymer is more significantly influenced by applied load and sliding speed values under dry sliding condition rather than lubricant media condition. Furthermore, the coefficient of friction and specific wear rate increases with the increase in applied load and speed values. This increase is much pronounced under dry sliding condition. Moreover, for the range of load and speed values of this study the specific wear rate using egg albumen lubricant registered lower values than that of the distilled water lubricant and the dry conditions. Finally, the specific wear rate values for GUR 1020 medical grade UHMWPE polymer under dry, water lubricant and egg albumen lubricant conditions are at the levels of 8x10-14, 1.4x10-14 and 0.5x10-14m2/N respectively. Key words: Medical Grade UHMWPE, tribology, distilled water, wear.

Tribological behavior of an ultrahigh molecular weight polyethylene in lubricated environments

AbstractThe wear and friction performance of GUR 1020 grade ultrahigh molecular weight polyethylene (UHMWPE) polymer was studied in distilled water, HASS (Hank’s balanced salt solution) and several protein lubrication environments. Wear tests were carried out using polymer pin -on AISI 304L stainless steel disc apparatus. Tests conditions were room temperature, 40N, 80N and 120N applied loads and 0.5 m/s sliding speed. For the range of load and speed value of this work, the coefficient of friction and wear rate for UHMWPE polymer decreases with the increase in applied load values. The coefficient of friction is highest and the specific wear rate values is lowest under HASS +HA solution lubricant. The average specific wear rate values for UHMWPE polymer under distilled water and HASS+HA (Hank’s balanced salt solution with Hyaluronic acid) lubrication conditions are in the order of 9x10-15 m2/N and 3x10-15 m2/N respectively. The wear mechanism includes abrasion and adhesive processes.

Tribological Performance of POM, PTFE and PSU Composites Used in Electrical Engineering Applications

In this experimental study, the tribological performance of polysulfone, poly-tetra-fluoro-ethylene, poly-oxy-methylene composites sliding against a poly-phenylene-sulfide polymer composite was studied. Tribological experiments were run under dry ambient conditions and at sliding speeds of 0.5–1.5 m/s under nominal load values of 20–40 N. Results for tested materials showed for the range of applied load and sliding speed values of this investigation that the friction coefficient and the wear rate are much more sensitive to the change in sliding speed rather than to the change in applied load values. The wear mechanism is mainly an adhesive process, but includes some abrasive process as well.

Deformation mechanism as a function of applied load under metal microindentation

The purpose of this paper was to estimate the contribution of applied load values to the development of deformation process during the quasi-static microhardness testing. Water pipes of the commercial iron alloys, steel and cast iron of various diameters (Ø 25–500 mm) were used for the investigation. It was established that H = f( P) curves for the metal samples can be divided into three specific parts (stages). The existence of those stages indicates that microindentation process occurs in polycrystalline metals due to different mechanisms of plastic deformation. They are: (i) the translation slip mechanism ( microlevel) for the 1st stage; (ii) translation/rotation slip mechanism ( mesolevel) for the 2nd stage; (iii) the crystal behaviour similar to a homogenous solid ( macrolevel) for the 3rd stage. It was shown that the coexistence of translation and rotation modes leads to their interaction and brings an important contribution into plasticity and brittleness of polycrystalline metals.

Tribological Performance of PTFE Bronze Filled Composites under Wide Range of Application Conditions

In this study, the friction and wear behavior of pure poly-tetra-fluoro-ethylene (PTFE) and bronze filled PTFE polymer composites at applied load values of 5, 10, 20, 30, 50, 100, 150, and 200N and sliding speed values of 0.32, 0.64, 0.96, 1.0, 1.5, and 2.0 m/s working conditions were examined. Friction and wear experiments were run at ambient conditions using a pin-on-disc test rig. The results for pure PTFE and bronze filled PTFE composites showed that under light working condition, the friction coefficient decreases with the increase in applied load values, while under severe conditions the materials showed less sensitivity to the change in applied load values. Furthermore, among tested materials the lowest wear rate is for bronze filled PTFE composite. The specific wear rate for pure PTFE and 60% bronze filled PTFE are in the order of 10-13 and 10- 15 m2/N, respectively. For the range of applied load and sliding speeds used in this investigation, the friction coefficient and wear rate showed very little sensitivity to the change in sliding test speed and large sensitivity to the change in applied load values. Finally, the wear mechanism of PTFE and PTFE composites include adhesive and deformation mechanisms.

Tribological Performance of Polymer Composites used in Electrical Engineering Applications

Dry sliding wear characteristics of commercially available poly-ether-imide (PEI)+20% ( glass fiber reinforced)GFR and polysulfone (PSU)+20% GFR polymer composite in use in electrical engineering applications were investigated using a pin―on―disc rig. Pin materials are (PEI)+20% GFR and PSU+20% GFR polymer composite. Disc materials are AISI 4140 steel and PA 46+30%GFR polymer composite. Wear tests were carried out at 0.5 and 1.0 m/sec sliding speeds and 20, 40 and 60N load values and under atmospheric conditions of temperature and humidity. Different combinations of rubbing surfaces were examined and the dynamic friction coefficient and specific wear rate values were obtained and compared. For all material combinations, the coefficient of friction shows little sensitivity to sliding speed and applied load values and large sensitivity to material combinations. For specific wear rate, PEI composite has shown little sensitivity to change in load, speed and materials combination while PSU composite shown large sensitivity to the change in load and material combinations. The friction coefficient of PEI+20%GFR and PSU+20GFR rubbing against AISI 4140 steel disc is a round 0.3 and is about 0.12 as rubbing against PA 46+30%GFR. The specific wear rate for PEI and PSU composites are in the order.of 10 -15 to 10 -14mm3 /N.m. The wear mechanisms are a combination of adhesive and abrasive wear.

The Effect of Test Parameters on Friction and Wear Performance of PTFE and PTFE Composites

The friction and wear properties of pure poly-tetra-fluoro-ethylene (PTFE), 35% carbon filled poly-tetra-fluoro-ethylene (PTFE+35%C), and 17% glass fiber-reinforced poly-tetra-fluoro-ethylene (PTFE+17%GFR) sliding against stainless steel under dry sliding conditions were studied by using a pin-on-disc tribometer. The effect of applied pressure and sliding speed on tribological properties of the polymer-stainless steel combination under dry sliding conditions was investigated. Tests were carried out at sliding speeds of 0.32, 0.64, 0.96, 1.0, 1.5, and 2.0 m/s and under applied pressures of 0.17, 0.34, 0.68, 1.02, 1.76, 3.53, 5.30, and 7.07 MPa. Optical microscopy was utilized to examine the worn surfaces of pure PTFE and it’s composite. The results indicated that, for pure PTFE, carbon-filled PTFE and glass fiber-reinforced PTFE composites are used in this investigation; the friction coefficient decreases with the increase in applied load values. The maximum reduction in wear rate was obtained by glass fiber-reinforced PTFE composite. The specific wear rate for pure PTFE, carbon filled PTFE composite, and glass fiber-reinforced PTFE composite were in the order of 10-13, 10-14, and 10-15 m 2/N, respectively. The wear mechanism include adhesive and abrasive processes.

Evaluation of the Performance of H3BO3-filled Polyamide Composite

In this study, the performance of boric acid (H3BO3)-filled polyamide composites were studied and evaluated at dry-sliding friction conditions. Wear tests were carried out using configuration of composite pin on a rotating AISI D2 steel disc. Test conditions were atmospheric conditions, 10, 30, 50 N applied load values, and 0.4, 0.80, 1.20 m/s sliding speeds. The results show a large drop in the coefficient of friction of PA6 with the addition of H3BO3 filler and a significant change in specific wear rate. Furthermore, the coefficient of friction decreases while the specific wear increases with the increase in sliding speed and applied load values, respectively. Moreover, for the range of load and sliding speed values in this study, the coefficient of friction also registered lower values with the increase in H3BO3 content percentage. The influence of boric acid on the coefficient of friction and wear is more pronounced at severe working conditions. Finally, the coefficient of friction of H 3BO3-filled composite is a round 0.1 value and its specific wear rate is in the order of 10—4 m3/N m.

Study of Abrasive Wear Volume Map for PTFE and PTFE Composites

The potential of this work is based on consideration of wear volume map for the evaluation of abrasive wear performance of polytetrafluoroethylene (PTFE) and PTFE composites. The fillers used in the composite are 25% bronze, 35% graphite and 17% glass fibre glass (GFR). The influence of filler materials, abrasion surface roughness and applied load values on abrasive wear performance of PTFE and PTFE composites were studied and evaluated. Experimental abrasive wear tests were carried out at atmospheric condition on pin-on-disc wear tribometer. Tests were performed under 4, 6, 8 and 10 N load values, travelling speed of 1 m/sec and abrasion surface roughness values of 5, 20 and 45 µm. Wear volume maps were obtained and the results showed that the lowest wear volume rate for PTFE is reached using GFR filler. Furthermore, the results also showed that the higher is the applied load and the roughness of the abrasion surface, the higher is the wear rate. Finally it is also concluded that abrasive wear process mechanism include ploughing and cutting mechanisms.

Dry sliding performance of thermoplastics against reinforced unsaturated polyester (BMC): In use in electrical contact breakers components

This work presents an experimental investigation of the wear and friction behaviours of reinforced thermoplastics in use in electrical contact breakers components. Sliding experiments were carried out on a pin-on-disc machine and under dry sliding conditions. The contact configurations used are polyamide 46 (PA46 + 30%GFR), polyamide 66 (PA66 + 30%GFR), polyoxymethylene (POM), polyphylenesulfide (PPS + 30%GFR) and aliphatic polyketone (APK) polymers pins against 15% long glass fibre reinforced unsaturated polyester (BMC) disc. The influences of applied load on the sliding wear behaviour of polymers were studied to decide the most suitable engineering polymer for contact breakers component in the electrical industry. The results showed that the coefficient of friction of the above polymers decreases linearly with the increase in load values. Furthermore, their specific wear rates increases with the increase in applied load values. The specific wear rate for APK, POM and PA66 + 30%GFR are in the order of 10 −8, 10 −8 and 10 −7 mm 3/N mm, respectively. The specific wear rates for PA46 + 30%GFR and PPS + 30%GFR are in the order of 10 −6 mm 3/N mm. Finally it is concluded that APK polymer is the most suitable engineering polymer for use in electrical contact breakers components.

Application of the continuous indentation test method for the characterization of mechanical properties of B4C/Al composites

The principal aim of the present study was to apply the continuous instrumented indentation testing with the Oliver-Pharr method for analysing the load-depth data in determination of mechanical properties of boron carbide/aluminium composites. The indentation tests were carried out at different applied load values (from 10 to 100 N) using Zwick 2.5/TS1S machine and a Vickers indenter. The hardness and reduced elastic modulus of composites were estimated from the unloading part of the indentation curve. The Vickers hardness numbers were compared with those obtained using conventional indentation, performed with Indentec 5030 SKV hardness tester.

An experimental investigation of dynamic crack propagation in a brittle material reinforced with a ductile layer

The fracture behavior of a dynamically loaded edge crack in a brittle-ductile layered material, as a function of applied loading rate, was experimentally investigated. Layered specimens were prepared by sandwiching a thin layer of ductile aluminum between two thick layers of brittle Homalite-100. The layers were bonded using Loctite Depend 330 adhesive, and a naturally sharp edge crack was introduced in one of the Homalite-100 layers. These single-edge notched specimens were loaded in dynamic three-point bending using a modified Hopkinson bar. The fracture process was imaged in real time using dynamic photoelasticity in conjunction with digital high-speed photography, and the applied load and load-point displacement histories were determined from the strain signals recorded at two locations on the Hopkinson bar. The results of this study indicated two distinct mechanisms of dynamic failure, depending on the applied loading rate. At lower loading rates, the starter crack arrested on reaching the aluminum layer and then caused delamination along the aluminum–Homalite interface. On the contrary, as the loading rate was increased, interfacial delamination was followed by crack re-initiation in the Homalite layer opposite to the initial starter crack. It was determined that the times required for crack initiation, delamination and crack re-initiation decreased as the loading rate was increased. However, it was also observed that the applied load values associated with each event increased with increasing loading rate. These observations indicate that both the dynamic failure process and plausibly the failure mode transition are affected by the rate-dependent properties of Homalite, aluminum and the interfacial bond. Finally, based on the measured peak loads and the observed failure mechanisms it was concluded that the incorporation of a thin ductile reinforcement layer can increase both the overall fracture toughness and strength of a nominally brittle material.

Modeling of the thermomechanical behavior of porous shape memory alloys

Abstract Two methods are used in this work to estimate the porous shape memory alloy (SMA) thermomechanical behavior. The porous SMA is assumed to be made of two components, the dense SMA matrix and the pores. An existing rate-independent type constitutive model is employed to describe the matrix behavior. Two contrasting strategies are used to estimate the overall thermomechanical behavior: (1) the unit cell finite element method (UCFEM) to account for periodic distribution of pores in the SMA matrix, and (2) an averaging micromechanics method based on the incremental formulation of the Mori–Tanaka method to account for random distribution of pores in the matrix. Cylindrical and spherical shapes are considered as approximations of open and closed pores, respectively, in both methods. Results are presented for both types of pores and comparisons are made between the two methods under various loading conditions. Both methods compare well in predicting the isothermal elastic material properties and pseudoelastic response under axial and out-of-plane shear loading. However, the transformation results differ under transverse and in-plane shear loading. This difference is found to be due to the use of an average value of stress for the SMA matrix in the micromechanics averaging method, which diminishes the effect of local stress concentration thereby delaying the onset of phase transformation caused by an applied load. On the other hand, the actual values of stress at all material points in the SMA matrix are used in the UCFEM causing phase transformation in regions near the pores at smaller applied load values than what is calculated by the micromechanics averaging method.

A mathematical approximation for the solution of a static indentation test

The classical contact problem of the indentation of a thin compressible linear elastic layer bonded to a rigid substrate is considered. Closed-form mathematical approximations of the deformation are presented for the cases of plane indentation by a rectangular block and three dimensional indentation by a plane-ended (axisymmetric) cyclinder. The approximations are analyzed in the context of a static indentation test by comparison of applied load values to those obtained using a classical integral transform solution. In the case of plane indentation, the mathematical and classical predictions agree to within 2% relative error for aspect ratios between 0.1 and 1.0 and apparent Poisson ratio between 0.0 and 0.3. Comparisons for the axisymmetric case indicate a similar pattern. The main advantage of the new approach is that it yields closed-form approximations of the static indentation solution which can also capture the essential singular behavior.

The effect of load on the cohesive strength of virgin surfaces of plastic metals

Virgin surfaces of copper, carbon steel, brass and lead have been obtained by the method of controllable internal breakdown. These surfaces have been found to feature high values of the cohesion coefficient which is, however, different for different materials. Cohesive strength is found to be a linear function of the applied load value in the load interval up to 0.6 H v. In the case of lead the linearity is shown to fail in the range of load values exceeding 0.6 H v. No failure of cohesion due to elastic stress relief was observed under the experimental conditions.