Restraining Forces Research Articles

Equivalent drawbead models for sheet forming simulation

Equivalent drawbead models associated with drawbead types, with which the geometrical modeling of drawbeads can be replaced in a numerical simulation of the stamping process, are introduced. The accuracy of the equivalent drawbead models rapidly computing the drawbead restraining and opening forces, based on the hybrid membrane/bending method accommodating Barlat’s anisotropic yield function for the plane stress state and the modified Chaboche model considering the Bauschinger effect and transient behavior under the plane strain condition, is verified by comparing the equivalent drawbead forces with those obtained from the finite element simulation. Moreover, the drawbead forces computed by equivalent drawbead models are employed in a finite element simulation of the automotive fender stamping process, from which the effectiveness and applicability of equivalent drawbead models are observed by comparing strains and draw-ins with those measured in the tryout panel.

등가 드로비드 모델의 실험적 검증 및 차체 스탬핑 해석에 적용

An equivalent drawbead model(EDM) for sheet metal forming analysis, which replaces complex drawbead geometries with drawbead forces in modeling the stamping dies with finite elements, is experimentally verified and applied to the numerical simulation of auto-panel stamping process. The drawbead restraining and opening forces of elliptical drawbead, circular drawbead, square drawbead, and step drawbead are obtained by performing the drawbead pulling test and compared with those of EDM and commercial code models(CCM). Better agreement with experimental measurements is found in EDM than CCM. Furthermore, the excellence of EDM is demonstrated in its application to the auto-body stamping analysis.

The paradox of change: how to coach while dealing with fear and uncertainty

PurposeThe purpose of this paper is to provide guidance for individuals who are learning to help others make significant changes in their lives.Design/methodology/approachThe paper is based on the author's own work and observations of how people change.FindingsIt was found that in order to create significant change it is necessary to build an effective relationship with the client, understand the restraining forces that hold the status quo in place and have an effective problem‐solving methodology.Research limitations/implicationsThe paper is not based on formal research. More research on the fastest way to build change skills is needed.Practical implicationsBy following the methodology here a coach can significantly improve the chances of a successful outcome when working with the client on a problem.Originality/valueThe paper will be of use to anyone who works with others to solve problems.

자동차 스템핑 금형의 드로우비드력 특성에 관한 연구

The drawbeads, which are used for controlling the flow of the sheet into die cavity by imposing the tension and for preventing the forming defects like wrinkling, springback, etc. during the sheet forming process, affect the formability strongly because of the differences in the restraint and opening forces according to the drawbead shapes and dimensions. In this study, the experimental device enabling to measure the drawbead restraining and opening forces is manufactured and the drawing forces of circular, square, and step drawbeads are measured. The drawbead restraining and opening forces of a circular drawbead are increased as its drawbead height is increased. Similarly, those of a square drawbead are increased as its height is increased and shoulder radii decreased. The drawbead forces obtained from the experiment were compared with those calculated in the numerical simulation of stamping process of automotive fender. Good agreement was found so that the experimental measurements can be used in the simulation of auto-body stamping process.

Chest Pain among Combat Veterans: A Conceptual Framework

This article describes the decision-making processes regarding seeking treatment for the symptom of chest pain in a population of combat veterans with post-traumatic stress disorder and panic disorder. Qualitative methods and standardized tools were used to explore the prehospital experiences of combat veterans who met diagnostic criteria for post-traumatic stress disorder, panic disorder, and admission to a coronary care unit for the symptom of chest pain. Semistructured audiotaped interviews were conducted. Obtaining medical treatment for the chest pain was dependent on internal and external motivating forces outweighing internal and external restraining forces in the decision-making process. The experience of military training influenced responses because of the expectation of self-reliance. A conceptual model emerged from the data that described the influences and restraints in seeking medical treatment.

Clinical and radiological outcome of medial patellofemoral ligament reconstruction with a semitendinosus autograft for patella instability

Recurrent patellar instability is a common problem after dislocation. The medial patellofemoral ligament (MPFL) contributes 40-80% of the total medial restraining forces. This study assessed the clinical and radiological outcome after a follow-up of 4 years after linear MPFL reconstruction using an ipsilateral Semitendinosus tendon autograft. 15 knees in 12 patients were examined with a mean of 47 months after linear reconstruction of the MPFL at a mean age of 30 years. 3 knees underwent previous surgery. 3 patients had mild trochlear dysplasia grade I or II, according to the classification of Dejour. If preoperative tibial tuberosity-trochlear groove distance (TTTG) was more than 15 mm, patients underwent additional medialisation of the tibial tuberosity (n=8) creating a similar postoperative situation for all patients. All patients were available for a postoperative evaluation, which consisted of a subjective questionnaire, the Kujala score, and the recording of potential patellar redislocation and apprehension. Patellar height and tilt was measured on plain radiographs. Postoperative CT scans were performed in patients with an additional tibial tuberosity-transfer. Postoperatively, one patient reported on recurrent bilateral redislocation. Physical examination however revealed no findings. Three knees presented with persistent patellar apprehension. Thirteen knees had improved subjectively after surgery. The mean Kujala score improved significantly from 55.0 to 85.7 points. The patellar tilt decreased significantly from 11.3 degrees to 9.2 degrees. Four knees had patella alta preoperatively, but only two at the latest follow-up visit. Previous surgery or additional trochlear dysplasia had no influence on the clinical outcome. MPFL reconstruction improves clinical symptoms, reduces the patellar tilt substantially, and may correct patella alta. Additional mild trochlear dysplasia did not compromise the outcome; however, this fact needs further attention in a larger study group.

Transforming Restraining Forces Into Driving Forces: An Example of a Bottom-Up Type of Integration.

Transforming Restraining Forces Into Driving Forces: An Example of a Bottom-Up Type of Integration.

Influence of constant and variable restraining force on springback of TRIP700 and stainless steel grades

Newly developed high strength steels (HSS) like dual phase (DP) and transformation induced plasticity (TRIP) grades as well as austenitic grades like AISI 304 and AISI 301 show superior strength compared to the microalloyed grades with the same formability (e.g. HSLA340). However, due to the multiphase microstructure and the austenite martensite transformation during forming, a higher springback will appear.In this paper the influence of different process parameters of six high strength steels on springback after stamping is investigated. The material properties were determined with uniaxial tensile tests. A modified Duncan Shabel test was used to draw U‐profiles with a controlled restraining force. To investigate different process parameters, constant restraining forces of 1 and 5kN and die radii of 3, 6, 9, and 12 mm were applied. In a second step, a shape set process was used. A constant restraining force of 1kN was used until a draw depth of 80 % was reached. Then the restraining was increased to 5.5 kN. The springback and the sidewall force were measured and analysed. An increased restraining force and a reduced die radius increases the sidewall force and reduces the springback. This resulted in a significant decrease in springback. The tests with variable restraining forces, also known as shape set process have shown that it combines a good formability with a reduced springback.

Phylogenetic autocorrelation under distinct evolutionary processes.

I show how phylogenetic correlograms track distinct microevolutionary processes and can be used as empirical descriptors of the relationship between interspecific covariance (V(B)) and time since divergence (t). Data were simulated under models of gradual and speciational change, using increasing levels of stabilizing selection in a stochastic Ornstein-Uhlenbeck (O-U) process, on a phylogeny of 42 species. For each simulated dataset, correlograms were constructed using Moran's I coefficients estimated at five time slices, established at constant intervals. The correlograms generated under different evolutionary models differ significantly according to F-values derived from analysis of variance comparing Moran's I at each time slice and based on Wilks' lambda from multivariate analysis of variance comparing their overall profiles in a two-way design. Under Brownian motion or with small restraining forces in the O-U process, correlograms were better fit by a linear model. However, increasing restraining forces in the O-U process cause a lack of linear fit, and correlograms are better described by exponential models. These patterns are better fit for gradual than for speciational modes of change. Correlograms can be used as a diagnostic method and to describe the V(B)/t relationship before using methods to analyze correlated evolution that assume (or perform statistically better when) this relationship is linear.

Heat Straightening Damaged Steel Plate Elements

The fundamental element of any structural steel shape is the flat plate. Damage to bridge structures consists of these plate elements, in combination, bent about their strong and/or weak axes. The purpose of this paper is to describe experimental and analytical research on heat straightening as applied to plates and to present related engineering criteria for its use. An experimental program was conducted to evaluate the response of plates to heat straightening and to identify important parameters influencing behavior. Over 300 heats were applied to a variety of plates. The primary factors influencing straightening were the angle of the vee heat, steel temperature during heating, and external restraining forces. The plastic rotation after heating was directly proportional to these parameters. To aid engineers in predicting plate movements during heat straightening, a simple mathematical formula was developed. This equation relates the average plastic rotation per vee heat to vee angle, steel temperature, magnitude of restraining force, coefficient of thermal expansion, and yield stress. The formula compares well to the experimental data and is the first simple formula available that includes the parameters of heating temperature and magnitude of restraining force. The form of this analytical approach also will lend itself toward extensions, including the behavior of rolled shapes, axially loaded members, and composite and noncomposite girders.

A simple model for the influence of push-morainal banks on the calving and stability of glacial tidewater termini

AbstractPush-morainal banks at the grounding lines of tidewater termini of temperate glaciers are the source of two types of restraining forces operating at the glacier terminus. Horizontal normal forces derive from the lateral support and transport of the bank of sediment at the terminus, whereas a horizontal shear force operates along the base of a bank pushed in front of an advancing glacier. The simple model we present suggests that bank-related restraining forces are significantly larger than the restraining force derived from the hydrostatic pressure of water adjacent to the submerged terminus of a glacier. During glacier advance, restraining forces continually increase, resulting in decreasing flow rates, glacier thickening and the eventual cessation of advance. During retreat, restraining forces continually decrease, resulting in increasing flow rates, glacier thinning and the potential for unstable, rapid, sustained retreat. The normal, seasonal, oscillatory advance retreat cycle of a glacier is moderated by restraining forces associated with push moraines. Unstable retreat is likely initiated when bank-related restraining forces fall below some threshold value during the seasonal retreat cycle. Calving is not a primary cause of glacier retreat, but is more likely a short-term response to increased flow rates. Increased flow rates result in glacier thinning and an approach toward buoyancy, both of which fluctuate seasonally in accordance with bank-related restraining forces.

A simple model for the influence of push-morainal banks on the calving and stability of glacial tidewater termini

AbstractPush-morainal banks at the grounding lines of tidewater termini of temperate glaciers are the source of two types of restraining forces operating at the glacier terminus. Horizontal normal forces derive from the lateral support and transport of the bank of sediment at the terminus, whereas a horizontal shear force operates along the base of a bank pushed in front of an advancing glacier. The simple model we present suggests that bank-related restraining forces are significantly larger than the restraining force derived from the hydrostatic pressure of water adjacent to the submerged terminus of a glacier. During glacier advance, restraining forces continually increase, resulting in decreasing flow rates, glacier thickening and the eventual cessation of advance. During retreat, restraining forces continually decrease, resulting in increasing flow rates, glacier thinning and the potential for unstable, rapid, sustained retreat. The normal, seasonal, oscillatory advance retreat cycle of a glacier is moderated by restraining forces associated with push moraines. Unstable retreat is likely initiated when bank-related restraining forces fall below some threshold value during the seasonal retreat cycle. Calving is not a primary cause of glacier retreat, but is more likely a short-term response to increased flow rates. Increased flow rates result in glacier thinning and an approach toward buoyancy, both of which fluctuate seasonally in accordance with bank-related restraining forces.

Effect of inotropic and vasodilator therapy on left ventricular diastolic filling in dogs with severe left ventricular dysfunction

Inotropic and vasodilator therapy for congestive heart failure improve left ventricular systolic performance by different mechanisms. However, the nature and extent to which diastolic filling is altered have not been well described. Acute severe left ventricular dysfunction was induced in 21 dogs by severe left ventricular global ischemia produced by left main coronary artery microsphere embolization until left ventricular end-diastolic pressure was ≥18 mm Hg. Dobutamine was infused in seven dogs until the peak positive first derivative of left ventricular pressure (dP/dt) increased by ≥33%. Nitroprusside was infused in seven dogs until left ventricular end-diastolic pressure was <15 mm Hg. Seven dogs were observed for 1 h after the induction of acute severe left ventricular dysfunction and served as the control group.In all groups of dogs, severe left ventricular dysfunction resulted in left ventricular dilation, reduction in area ejection fraction, elevation of left ventricular end-diastolic pressure and an early redistribution of diastolic filling (increased 1/3 and 1/2 filling fractions) despite a markedly abnormal tune constant of relaxation. No changes were noted in any variable after 1 h of observation in the seven control dogs. Nitroprusside reduced left ventricular size and filling pressure, increased cardiac output, improved relaxation and redistributed diastolic filling to later in diastole as characterized by a reduced 1/3 filling fraction (19.4 ± 7.4% versus 51.4 ± 10%, p < 0.001). The pressure-area curve was shifted downward and leftward. Dobutamine increased cardiac output, increased area ejection fraction, reduced end-systolic volume, improved relaxation and redistributed diastolic filling to later in diastole (1/3 filling fraction 18.7 ± 7.4% versus 44.2 ± 8.0%, p < 0.001). The pressure-area curve was shifted downward and leftward initially (smaller end-systolic volume and lower left ventricular minimal pressure).In conclusion, despite differing mechanisms utilized to improve systolic and diastolic performance, diastolic filling was altered in a similar fashion by both dobutamine and nitroprusside. The nonspecificity of this alteration may be related to similar influences of improved relaxation and reduced pericardial restraining forces on the diastolic filling pattern.

Casing Deformation in Ekofisk

Casing deformation resulting from reservoir compaction occurred in the Ekofisk field operated by Phillips Petroleum Co. Norway and is a serious problem in three of the fields. This study established a relationship between reservoir compaction and casing failure by statistical analyses, finite-element modeling (FEM), and the analyses of deformed casing and logs run through collapsed casings. Ekofisk casing deformation is related primarily to the near well incremental strain, well inclination, and casing diameter. Useful correlations to estimate future probabilities of casing deformation as a function of reservoir variables and well parameters were also obtained. The authors concluded that casing failure induced by reservoir compaction can be minimized through a pressure-maintenance program to reduce strain by drilling with the highest practical angle and by using the largest possible casing in the well.

The uprighting effect of the Fränkel appliance on the mandibular canines and premolars during eruption

The effect of the Fränkel (FR) appliance on the eruptive path of the mandibular canines and premolars was evaluated in patients who were monitored from 8 to 13 years of age. The sample treated with the FR appliance consisted of 84 subjects with Class I or Class II malocclusion associated with crowding in the mandibular dental arch. Twenty-seven subjects of approximately the same age and with almost an indentical space deficiency in the mandibular arch not subjected to FR treatment served as a comparison group. Permanent teeth were not extracted during treatment in any cf the subjects in either group. The primary criterion of patient selection was based on the availability of standardized serial lateral and posteroanterior cephalograms, permitting an exact identification of the canine and premolar contours during eruption. Increases in width between the tips of the mandibular canines and the buccal tips of the mandibular premolars during eruption were significantly greater in the FR group than in the comparison group ( P < 0.001). The expanding effect of the FR appliance was evidenced particularly in the region of the mandibular first premolars. The distance between the buccal tips of these teeth increased by an average of 3.5 mm more in the FR group than in the comparison group. Likewise, the width between the root landmarks of the first mandibular premolars increased during eruption in the FR group 2 1 2 times more than in the untreated sample, a difference that was statistically significant ( P < 0.01). The analysis of the lateral cephalograms showed that the tips of the mandibular canines moved distally during eruption in the comparison group significantly more (mean = 2.2 mm) than in the FR group ( P < 0.01). There was also a significant intergroup difference in the anteroposterior changes of point B, which moved posteriorly in the FR group less than in the untreated sample ( P = < 0.01). This comparative study indicates that the eruptive path of the mandibular canines and premolars during treatment with the FR appliance can be significantly influenced in lateral, anteroposterior, and vertical dimensions. Since the FR appliance did not contact the mandibular teeth, it is suggested that the intercanine expansion in the treated group was the result of the vestibular shields that eliminated the restraining forces of the external muscular environment. The results of the study suggest that the size and shape of the external soft-tissue capsule are an important space factor controlling occlusal development, which should be considered when discussing the postretention recurrence of mandibular crowding. The FR appliance appears to be a suitable orthopedic exercise device for correcting a hypertonic pattern in the circumoral capsule; it provides an undisturbed dentoalveolar development in the critical period of eruption.

Modify the Restraining Forces Address of the Chairman

Modify the Restraining Forces Address of the Chairman

Address of the Vice President: Modify the Restraining Forces

Address of the Vice President: Modify the Restraining Forces

Free Transverse Vibration of Flat Slabs

The free transverse vibrations of a rectangular plate simply supported along the periphery and rigidly connected to its interior columns is solved by subdividing the structure into elementary components-the plate and columns, and replacing connections between these components by harmonic restraining forces at the connections. The conditions of continuity of the original structural system provide the equation from which the natural frequencies of the plate can be obtained. Examples are presented to illustrate the approach and to show the effect of bending stiffness of the supporting columns on the natural frequencies of the system.

An analysis of counterwashers for freeze-distillation desalination

A hydrodynamic model based on Darcy's law is developed for flooded counterwashers of the type used in washing brine from ice crystals. In the model the brine is displaced by fresh water from the interstices of the ice plug. Similarity parameters which can be used for comparing the performance of different counterwashers are derived. Both analytic and numerical solutions are presented. The production rate of fresh water is found, for example, to increase with an increase in the ice crystal size, the ice plug length above the screens, the concentration of ice crystals in the slurry, and the external mechanical restraining forces on the ice plug. It is also found to increase with a decrease in the ice plug length below the screens, where this length is shown to be an independent parameter of the problem under certain slurry feed conditions, such as gravity feed. Design criteria are presented for minimizing the capital cost for a given production rate.

Critical Flow Velocities for Collapse of Reactor Parallel-Plate Fuel Assemblies

Theoretical formulas are presented for prediction of the flow velocity at which collapse occurs in long parallel-plate assemblies. Beyond the critical velocity the pressure-unbalance forces, developed as a consequence of a small deflection, exceed the corresponding elastic restraining forces, and the plates collapse. Both flat and curved-plate assemblies are considered, and the applicability of the formulas to design of reactor fuel-plate assemblies is discussed.