Bolted Joint Analysis Form

Active Component

The active component is reported in the blue header at the top-right of the form. For this example, the active component is Component #181212.

Concept

The concept entry defines which unique panel concept, for the selected panel family, has a hole. Since multiple panel concepts can be selected during optimization, the fastener hole can be defined in each desired panel concept.

Object

The object entry defines which specific panel object has a hole. For sandwich panels, a hole can be defined in each facesheet. For stiffened panels, a hole can be defined in each stiffener or skin object.

Object has one or more holes

This option must be selected to define the presence of a hole and activate the bolted joint analysis for the selected panel concept and panel object.

The Fastener frame defines geometric details about the fastener.

Description

The fastener description permits each fastener to be given a unique name. This entry does not affect the bolted joint analysis.

Diameter, D

The fastener diameter defines the diameter of the hole in the laminate; there is no extra tolerance added to this value during the bolted joint analysis.

Countersink Depth

The fastener countersink depth defines the depth of fastener countersink depth. This entry does not affect any HyperSizer analysis; it is used to classify the fastener.

Joint correction factors are used to correct the margins of safety for effects not captured in the FEM and analytical methods. During the fastener analysis, the bearing stress allowable F_bru is scaled by the cumulative correction factor, K_cf.

MS=	Fbru Kcf	– 1
	σbearing (fitting factor)

See Joint Correction Factors.

The fitting factor, K_f, is applied to the bearing force in the margin of safety calculation. This factor is used to account for uncertainties. A typical value for the fitting factor is 1.15.

The fastener load frame provides options for extracting or manually entering bearing force on a laminate.

You may choose one of three approaches for defining bearing force on the laminate.

• Manually enter bearing forces
• Compute bearing force from shear flow
• Automatically extract bearing forces from FEM

See Bearing Force.

Notice the blue text in the lower right corner of the frame identifies * as the user input that is not dependent on the active load cases and ** as the user input required to calculate the bearing force (P) from the shear load (q).

Joint Shear Load*, q

The joint shear load option permits you to manually enter the joint shear load. The bearing force is then calculated using the shear flow method. Since this value is user-defined, it is not load case dependent. (units = lb/in, N/m)

Joint Shear Load, q (From the Sizing form, load case dependent)

This option retrieves the object loads from the Sizing form to calculate the shear load. The bearing force is then calculated using the shear flow method. This process is performed for each load set.

Fastener Pitch**, S

The fastener pitch parameter is the spacing between the fasteners. This value is required for the shear flow method. Since this value is user-defined, it is not load case dependent. (units = in, m)

Fastener Rows**

The fastener rows parameter defines the number of fastener rows. This value is required for the shear flow method. This value is user-defined and is not load case dependent. The fastener rows must be defined as a positive integer. Note that for composite joints, the shear flow method becomes non-conservative if the number of fastener rows are less than two.

Bearing Force *, P

The bearing force option permits you to manually enter the bearing force. Since this value is user-defined it is not load case dependent. (units = lb, N)

Load Angle, α

The load angle defines the angle between the bearing force and the N_x load direction for the laminate. The N_x load direction is defined by the element material angle in a FEM.

The load angle only affects the BJSFM analysis methods. (units = degrees)

CBUSH Force, P

This option extracts bearing force from the FEA-computed CBUSH loads. During the bolted joint analysis, every CBUSH element attached to a grid on the active component is considered and the controlling fastener force is displayed in the Bearing Force *, P field.

This frame provides options to superimpose any component of a load into the bearing load or you may send any load component into the BJSFM methods as a bypass load. You may also ignore any component of the load for bolted joint analysis. HyperSizer will automatically compute the bypass loads from the object loads, bearing force, and load angle.

Note that the object loads displayed here are determined from the true average of the element loads in the component.

See Bypass Loads.

 

BJSFM Failure Method

During the BJSFM analysis, HyperSizer will use the selected lamina failure criteria to calculate ply-by-ply margins of safety around the laminate hole. Select from the traditional ply-based failure theories in the drop-down list.

Bearing stress allowables are defined as a function of percent 45 degree fibers. Also, lamina correction factors are applied to material properties, such as characteristic distances, ply stiffness, and stress/strain allowables. For this reason, it is valuable to see the optimum laminate geometry displayed in the Material frame.

There are three BJSFM analysis methods available: bearing and bypass load, bearing load only, and bypass load only. The results displayed in the BJSFM Analytical Results frame correspond to the controlling BJSFM analysis method. Note that the BJSFM analysis uses the uncorrected orthotropic material properties to generate the stress field. Also, HyperSizer uses uncorrected lamina allowables to compute the lamina strength margins of safety.

Shear Load, q

The Shear Load displays the controlling joint shear load used to calculate the bearing force during the BJSFM analysis. If the bearing force was discretely defined or extracted from the FEM, the displayed value will be zero. (units = lb/in, N/m)

Bearing Force, P

The Bearing Force displays the controlling bearing force used in the BJSFM analysis. The bearing force is calculated from the user-defined method. See Bearing Force.

Bypass Nx, Ny, Nxy

The bypass load options display the controlling bypass load used in the BJSFM analysis. The bypass loads are computed from the net result of applying bolt force and far field loading. See Bypass Load.

Load Set

The Load Set displays the controlling mechanical or thermal load set corresponding to all results displayed in the BJSFM analytical results frame.

Analysis Status

The Analysis Status displays status information about the last BJSFM analysis. If input variables such as hole diameter, laminate thickness, and fiber percentages are defined outside the bounds of the BJSFM method, warning information will be displayed.

Load Angle α

The Load Angle displays the load angle used during the BJSFM analysis. (units = degrees)

D0t, Tension

The characteristic distance, tension displays the controlling characteristic distance for the BJSFM analysis with tension bypass loads.

D0c, Compression

The characteristic distance, compression displays the controlling characteristic distance for the BJSFM analysis with compression bypass loads. See Characteristic Distance.

The characteristic distance is fundamental data passed from HyperSizer to the BJSFM bolt hole analysis routine. This lamina property defines the distance from the free edge/bearing surface at which the material strength analysis is performed.

Fbru, effective

The effective bearing allowable displays the effective bearing stress allowable backed out from the BJSFM margin of safety. (units = Ksi, MPa)

Note that the BJSFM HyperSizer margin includes the contribution of the bypass loads. This far field loading causes the hole to elongate, even without bolt bearing. If far field loading is present, it can have a significant impact on reducing the allowable bearing stress.

Margin-of-Safety*

The Margin-of-Safety displays the minimum BJSFM margin of safety from the active BJSFM analysis. This margin will correspond to the minimum BJSFM margin of safety displayed on the Failure tab.

See Laminate Stress Allowables.

Shear Load, q

The Shear Load displays the controlling joint shear load used to calculate the bearing force during the laminate bearing analysis. If the bearing force was discretely defined or extracted from the FEM the displayed value will be zero. (units = lb/in, N/m)

Bearing Force, P

The Bearing Force displays the controlling bearing force used in the laminate bearing analysis. The bearing force is calculated from the user-defined method. (units = lb, N)

Load Set

The Load Set displays the controlling mechanical or thermal load set corresponding to all results displayed in the laminate bearing analytical results frame.

Analysis Status

The Analysis Status displays status information about the last bearing analysis. If the bearing analysis is unsuccessful due to lack of information such as material properties, the appropriate warning information will be displayed.

Fbru, effective

The effective bearing allowable displays the effective bearing stress allowable used to calculate the laminate bearing margin of safety. To determine the effective bearing allowable, the pristine bearing allowable is interpolated from the laminate stress allowables and is multiplied by a cumulative correction factor. (units = Ksi, MPa)

Margin-of-Safety*

The Margin-of-Safety displays the controlling margin of safety from the laminate bearing analysis. The fitting factor is included in this calculation.