Contact Area Ratio Research Articles

Mutual Overlap Coefficient and Wear Debris Motion in Dry Oscillating Friction and Wear Tests

In oscillating dry friction and wear tests, mechanical parameters such as degrees of freedom and stroke amplitudes govern the formation of wear debris. A third body is formed by the wear debris within the contact. It is progressively eliminated from the contact area. The volume of wear debris lying outside the contact area corresponds to the total wear between the pin and the counterface. Wear is thus controlled by the elimination of wear debris outside the contact. The overlap of the pin and the friction track on the counterface thus controls the wear debris elimination. That overlap is characterized by the mutual overlap coefficient (MOC) which is defined as the ratio of the pin contact area to the counterface wear track. Wear debris formation and elimination was simulated with a pin made of a high-wear-rate material rubbing against an oscillating counterface. Widely different wear results and transfer film morphologies are obtained when the MOC varies between 0.66 and 0.99. Wear results are analyzed for small and large MOC. In this study, small values of MOC are defined as being less than 0.8 while large values of MOC are those greater than 0.9. Small and large values of MOC generate characteristic third bodies, and transfer film morphology depends on MOC and load. Related wear mechanism are discussed.

Computer Simulation of Elastic Rough Contacts

A computer program is developed to analyze the contact of a rigid smooth plane and computer-simulated elastic rough surfaces. The simulated surfaces have isotropic Gaussian height distribution and bilinear autocorrelation function. Results of two cases are presented: (1) dry contact between a square elastic rough punch and a rigid smooth plane; (2) dry contact between an elastic rough half-space and a rigid smooth plane. Force-compliance relationship is compared with hat derived by Bush, Gibson, and Thomas. Real contact area ratio Ar is found to be approximately proportional to nominal contact pressure in the range 0.025 < Ar < 0.3. Presented at the 39th Annual Meeting in Chicago, Illinois May 7—10, 1984

Effect of some variables on the migration of additives from plastics into edible fats

It has been shown that organic liquids such as alkanes and di-n-alkyl ethers are unsatifactory for use as fat simulants. A synthetic, analytically pure triglyceride mixture, which has a fatty acid and triglyceride distribution similar to that of coconut oil, has proved to be a universally applicable simulant for edible oils and fat-containing foodstuffs. The influence of temperature on the migration of additives from PVC, high-density polyethylene and polystyrene into edible oils and into this fat simulant, HB 307, has been studied. For all the polymer/additive combinations investigated, additive migration into the fat simulant increased markedly above a test temperature of 50°C. The intensity of this increase and the temperature at which it became apparent was found to depend on the type of plastic material and the physico-chemical properties of the additive. The amount of additive migrating is largely independent of the depth of the layer of HB 307 (i.e. the ratio of contact area to amount of simulant) as studies with simulant layers varying from 2·5 to 10·0 mm is depth showed. These results and others published elsewhere have been used to define conditions appropriate for the testing of plastics films and containers intended for packaging edible oils and fatty food-stuffs.

Effect of some variables on the migration of additives from plastics into edible fats

It has been shown that organic liquids such as alkanes and di- n-alkyl ethers are unsatisfactory for use as fat simulants. A synthetic, analytically pure triglycéride mixture, which has a fatty acid and triglyceride distribution similar to that of coconut oil, has proved to be a universally applicable simulant for edible oils and fat-containing foodstuffs. The influence of temperature on the migration of additives from PVC, high-density polyethylene and polystyrene into edible oils and into this fat simulant, HB 307, has been studied. For all the polymer/additive combinations investigated, additive migration into the fat simulant increased markedly above a test temperature of 50°C. The intensity of this increase and the temperature at which it became apparent was found to depend on the type of plastics material and the physico-chemical properties of the additive. The amount of additive migrating is largely independent of the depth of the layer of HB 307 (i.e. the ratio of contact area to amount of simulant) as studies with simulant layers varying from 2·5 to 100 mm in depth showed. These results and others published elsewhere have been used to define conditions appropriate for the testing of plastics films and containers intended for packaging edible oils and fatty food- stuffs.

単粒研削における研削力

In this report interference phenomenon between a grain groove and grinding force with the single grain passing through close the groove is researched theoretically and experiment-ally. Assuming that grinding force with a single grain consists of ploughing force and friction force, the factors which control grinding force may be approximately given with dynamic yield pressure of workmaterial, ratio of piling-up area, net contact area, friction coefficient and contact ratio between tool and workmaterial. Applying these factors, specific grinding force defined as grinding force per theoretical chip area can be shown as a function about pitch ratio γ, distance between ajacent tool-groove normalized by theoretical width of the groove. This theory approximately agrees with the experimental values obtained with a pyramidal diamond tool. To put this briefly, specific grinding force remains constant in approximately γ>3, but varies according to γ in approximately γ<3, taking the maximum value in γ≈1.51.7, the minimum value in 0.81.0, remarkably increasing as γ decreases furthermore, in other words, interference phenomenon is caused. The abovestated results suggest that interference phenomenon has much effect on abrasive working force.

1582. Aminopyrine: Poor cow?

Osteoarthritis (OA) of the knee joint is a common disease accompanied by pain and impaired mobility. Despite some recent concerns on the lack of correlation between the medial load and the knee adduction moment (KAM), KAM is routinely considered as a surrogate measure of medial load and hence a marker where its reduction is the main focus of preventive and treatment interventions.Determine the relative sensitivity of the tibiofemoral medial-lateral contact load partitioning to changes in the knee adduction angle (KAA) versus KAM.Using a lower extremity hybrid musculoskeletal (MS) model driven by gait kinematics and kinetics, we compute here in asymptomatic subjects the sensitivity of the knee joint biomechanical response (muscle and ligament forces) in general and medial/lateral load partitioning in particular to the relative changes in the reported KAA versus changes in reported KAM (both by one standard deviation).As KAA increased (at constant KAM), so did the passive moment resistance of the knee joint which as a result and at all stance periods substantially reduced forces in lateral hamstrings while increasing those in medial hamstrings. At 25% and 75% stance as two highly loaded periods of gait, the drop in KAA (from + SD to –SD while at constant KAM) drastically reduced the medial contact force by 44% and 30% and the medial over lateral contact load and area ratios by 92% and 79% as well as 64% and 51%, respectively. In contrast, the equivalent alterations in KAM (by ± SD at constant KAA) had lower and less consistent effects (<7%) showing much smaller sensitivity to changes in KAM alone. Ligament forces altered at various stance periods with inconsistent trends; peak values of 418 N in the anterior cruciate ligament (90% carried by the posterolateral bundle) and 1056 N in the patellar tendon were computed both at 25% stance and minimum KAA.These findings indicate a poor correlation between KAM and tibiofemoral load distribution suggesting instead that KAA and knee alignment should be in focus as the primary marker of knee joint load partitioning and associated prevention and treatment interventions.

1565. Synergizing chlorofluorohydrocarbon toxicity?

Osteoarthritis (OA) of the knee joint is a common disease accompanied by pain and impaired mobility. Despite some recent concerns on the lack of correlation between the medial load and the knee adduction moment (KAM), KAM is routinely considered as a surrogate measure of medial load and hence a marker where its reduction is the main focus of preventive and treatment interventions.Determine the relative sensitivity of the tibiofemoral medial-lateral contact load partitioning to changes in the knee adduction angle (KAA) versus KAM.Using a lower extremity hybrid musculoskeletal (MS) model driven by gait kinematics and kinetics, we compute here in asymptomatic subjects the sensitivity of the knee joint biomechanical response (muscle and ligament forces) in general and medial/lateral load partitioning in particular to the relative changes in the reported KAA versus changes in reported KAM (both by one standard deviation).As KAA increased (at constant KAM), so did the passive moment resistance of the knee joint which as a result and at all stance periods substantially reduced forces in lateral hamstrings while increasing those in medial hamstrings. At 25% and 75% stance as two highly loaded periods of gait, the drop in KAA (from + SD to –SD while at constant KAM) drastically reduced the medial contact force by 44% and 30% and the medial over lateral contact load and area ratios by 92% and 79% as well as 64% and 51%, respectively. In contrast, the equivalent alterations in KAM (by ± SD at constant KAA) had lower and less consistent effects (<7%) showing much smaller sensitivity to changes in KAM alone. Ligament forces altered at various stance periods with inconsistent trends; peak values of 418 N in the anterior cruciate ligament (90% carried by the posterolateral bundle) and 1056 N in the patellar tendon were computed both at 25% stance and minimum KAA.These findings indicate a poor correlation between KAM and tibiofemoral load distribution suggesting instead that KAA and knee alignment should be in focus as the primary marker of knee joint load partitioning and associated prevention and treatment interventions.

The Use of Analog Computers for Determining Surface Parameters Required for Prediction of Thermal Contact Conductance

The mathematical analysis of a thermal contact by Fenech and Rohsenow requires knowledge of certain parameters describing the geometry of the contact interface. These parameters are volume average thickness of the void above and below the plane of the contact, the number of contacts per unit area, and the ratio of the actual contact area to the total area. The authors outline a method for determining these parameters graphically. This paper describes a method for obtaining analog voltages of surface profiles of contacting surfaces and the application of a general purpose analog computer to determine the geometric parameters of contact as a function of contact pressure. The results of applying this method are combined with the analysis of Fenech and Rohsenow. The predicted contact conductance is found to agree well with experimental data at mean contact temperatures of 100, 200, and 300 F for load pressures of 100 to 20,000 psi.

切削機構に関する研究 (第1報)

From the experiments on the cutting of 0.4% carbon steel, in which cutting speed, rake angle, feed and workpiece temperature (hot machining) were varied, following relations were found : ω≡φ+β-α=f(α) … (1) m=kmt1sinω/sinφcosβ, km_??_2.0… (2).Notations are shown in Fig. 1.Applying the total reflection method to the cutting of lead by a glass prism, it was found that the ratio of the true tool-chip contact area to the apparent contact area, kc, was nearly equal to 1.Considering the balance of force and equation (2), the following was obtained.kcknτc/τs=sin2β/sin2ω, kckm_??_2.0… (3) where, τc and τs are the shear flow stress of the work material at tool face and shear plane. Then, τc and τs, which should be determined by the temperature, the strain and the strain rate at both zones, are known, β and φ can be determined from the equation (1) and (3).