Datum Mesh 0.3.3

Frames for everyday structural analysis: load cases and combinations, hinges, steel section tables.

Load cases and combinations

• Loads › Cases and Combinations: name load cases (dead, imposed, wind, …) and build combinations of them, each case times your own factor. The loads already drawn go into the first case.
• Pick a case or a combination on the Loads tab: only its loads are drawn, new loads go into the picked case, and Solve (and Buckling) solve it. The legend says which one the results are for. A load's case can be changed in the Inspector.
• Results › Envelope: every combination solved in turn, with each member's largest and smallest axial force, its largest shear, moment, twisting and deflection, its largest utilisation and the combination that gives it, and the range of every reaction.
• Datum Mesh does not apply a design code: the factors are yours.

Hinges

• A beam can have a hinge at either end (Inspector): it carries no bending moment there, as in a pinned beam-to-column connection. In 3D both bending moments are released; twisting is still carried, unless no rigid beam holds the node (a ball joint). Hinges act in the static solve, natural frequencies and buckling, and are drawn as small circles.

Steel section tables

• Sections › From the tables: European rolled IPE, HEA and HEB sections (56 sizes, EN 10365 nominal dimensions). Their properties are worked out from the dimensions with the root fillets (a new root radius for I-sections), and agree with the tables.

Examples and fixes

• New example: a two-storey braced steel frame with HEB columns, IPE beams pinned at their ends, a braced bay, three load cases and three combinations.
• Escape closes a dialog left open under one that has just closed (focus was lost).

Trust

• Help › Verification: 120 checks, all passing. New: benchmark 18, a beam hinged at both ends between fixed supports (simply supported: wL²/8, 5wL⁴/384EI, its natural frequency and, as a column, π²EI/L²), a beam with a hinge partway (statics), a 3D beam hinged both ways, a combination 1.35 G + 1.5 Q and its envelope against superposition, and the tables' second moments (IPE 300, HEA 200, HEB 200, within 0.01 %) and areas (all 56 within 0.5 %).
• Random frames now have hinges, and random load cases always add up: a combination's results equal its cases' results times their factors, in 2D and 3D.

Datum Mesh 0.3.2

Revolved 3D solids, a cutting plane through the results, and faces picked in 3D.

Revolved solids

• A 3D solid can now be revolved about the y axis instead of extruded (Inspector, with nothing selected): shafts, hubs, discs and vessels from their half-section, drawn right of the axis.
• Turn it a full 360°, or a sector (90°, say) with symmetry on its two cut faces, which are then the back and front faces. The section can reach the axis: the part is solid through its middle.
• New example: the pressure vessel revolved a quarter turn.

Supports

• Held directions: hold only x, y or z of a face (Loads › Hold Directions, or a support's Inspector).
• A support can be a line along a face at any fraction of the way through (Inspector › Where), as NAFEMS LE10 asks for.

3D view

• Click a face in the 3D view to put the support or load picked on it: a side face, or the back or front face.
• Cutting plane: once solved, cut across x, y or z (under the view) and slide the plane through the part; the inside is coloured by the result shown.

Trust

• Help › Verification: 105 checks, all passing. New: benchmark 17, a closed-end thick cylinder revolved a quarter turn and a full turn against Lamé (hoop stress 0.2 %, axial 0.7 %, bore movement 0.007 %), a round bar through the axis squeezed end to end (exact to 1 part in 10¹³), and NAFEMS LE10, the thick plate under pressure (σyy at D within 1.4 % of −5.38 MPa).
• Random 3D solids now include revolved ones (some through the axis, some a full turn), held directions and line supports: all 60 solve with their reactions balancing the loads, or say why they cannot.

Datum Mesh 0.3.1

Sketch tools: shape a part's section with rounds, bevels, cut-outs and patterns before it is solved.

Sketch tools (Geometry, and Format on a selected shape)

• Round Corners (fillet) and Bevel Corners (chamfer): any corner between two straight edges, one or all at once, at a typed radius or distance. ⌒ in the Inspector's corner table rounds just that corner.
• Union, Subtract and Intersect two shapes: click one, Shift+click the other. Arcs and circles stay true arcs and circles, so a support or load on a round edge is still on one edge. Rings left inside become holes. Supports and loads move to the edges they lie on, and an outline keeps its edge numbers where it can.
• Ready-made Slot, Rounded Rectangle and Regular Polygon from typed sizes, as a shape or a hole.
• Offset an outline in or out (a wall of a given thickness, a clearance round a hole); arcs keep their centres.
• Linear and Circular Patterns: copies of shapes in a row or round a centre (bolt circles), with the supports and loads on their edges.
• Every tool is one step to undo, and is in Tell Me (Ctrl+K).

Trust

• Help › Verification: 94 checks, all passing. New: benchmark 16, the areas of eight shapes made by the sketch tools against hand formulas (to 1 part in 10⁹), and the plate with a hole again, its hole cut by Subtract, giving the same stress concentration of 3.0.
• Random pairs of shapes (60 of them, circles, rectangles, slots and rounded rectangles) are combined all three ways: the areas always add up (union plus intersection equals the two shapes), and every result passes the model's checks and meshes.

Datum Mesh 0.3.0

3D solids: a part's outline extruded by its thickness and solved in 3D.

3D solids

• Home › 3D Solid: draw the outline and holes in Section, exactly as for a plane part, and set the thickness; the part is extruded along z and shown in the 3D view.
• Supports and loads go on faces: an edge in Section stands for its side face, and the back and front faces have their own buttons while a support or load is being placed. Fixed, roller and symmetry supports; pressures, face forces (now with Fz too) and gravity.
• The section's mesh is swept through the thickness in layers of wedges: 18-node wedges from the quadratic mesh (accurate), 6-node from the linear one. Layers are automatic, or set in the Inspector.
• Once solved, the surface is coloured by any of 14 results (von Mises, σ1, σ3, each stress and shear, the displacements, the safety factor) on the deformed shape; hover to read a value. The Results page and report give the largest and smallest values anywhere inside, with where, the reactions and the equilibrium check in six sums.
• New examples: the L-bracket as a 3D solid, and a blank 3D solid.

Quicker solves

• The sparse solver now uses every core of the computer, and big 3D models store half the matrix: about 90 000 unknowns of a 3D solid solve in about 6 s and 1.2 GB on four cores.
• A 3D solid is limited to 200 000 unknowns, with a message saying how to make the mesh coarser, so a too-fine mesh cannot run the computer out of memory.

Trust

• Help › Verification: 85 checks, all passing. New: a 3D patch test (a uniform stress reproduced to 1 part in 10¹⁴, with the thinning), a 3D cantilever against Timoshenko beam theory (0.005 %) and its bending stress, and a thick cylinder in 3D against Lamé (hoop stress 0.5 %, bore movement 0.003 %).
• Random 3D solids (40 of them) solve with their reactions balancing the loads in all six sums, or say why they cannot.

Datum Mesh 0.2.6

3D frames vibrate and buckle; the app starts lighter and keeps to size and speed budgets.

3D frames

• Solve › Natural Frequencies and Buckling now work for 3D frames: beams bend both ways and twist as they vibrate, and buckle by bending about either axis. The shapes swing in the 3D view; the lists, tables and printed report are as for plane frames.
• Truss bars in compression are checked on their own about their weaker axis.
• Buckling in 3D is by bending only: twisting and lateral-torsional buckling of open sections (I, channel) are not checked yet, and the Results page says so.

Lighter and quicker

• The 3D view's code loads only when a 3D frame is shown: the window starts with a third of the code it had (282 kB, was 863 kB).
• The fonts are bundled once, not twice (the window is 1.1 MB, was 1.2 MB).
• Size budgets checked on every build: the installer stays under 5 MB, the window's startup code under 400 kB.
• Solve times are in the verification record: the examples solve in milliseconds, a fine mesh of 141 000 unknowns in about 1.5 s, and six frequencies of a 12-storey 3D building frame (147 000 unknowns) in about 2.3 s.

Trust

• Help › Verification: 76 checks, all passing. New: a 3D cantilever's frequencies across its width, across its depth and in twisting; a column buckling about its weak and then its strong axis; and the portal frame in 3D, whose plane frequencies and buckling factors are found again to 1 part in 10¹².

Datum Mesh 0.2.5

• Windows now lists the publisher as Datum.

Datum Mesh 0.2.4

3D frames: frames and trusses in space, drawn on planes and seen in 3D.

3D frames

• Home › 3D Frame: beams that stretch, twist and bend about both axes of their section, and truss bars, anywhere in space. y is up and z is depth.
• Members are drawn on a working plane: Front (x-y), Side (z-y) or Plan (x-z), at a depth you pick or type; members off the plane are shown faint. The status bar reads x, y and z.
• The 3D view shows the whole frame with its supports and loads: turn it with the left button, pan with the right, zoom with the wheel; Front, Top and Iso buttons. Click nodes and members to select them, or to put supports and loads on them.
• Geometry › Repeat copies the selected members (or the whole frame) a step along any direction, with their supports and loads, and joins the copies with beams or truss bars: draw one frame, repeat it into bays.
• The Inspector takes z for nodes, Fz and moments about x, y and z, member loads along z, gravity in z, springs in all six directions, and the roll of a beam's section about its axis.
• Sections give the second moment about the other axis and the torsion constant J (thin-walled formulas for boxes, I and channel sections; your own values for custom sections).

Results in 3D

• Once solved, the members are drawn on their deflected shape and coloured by utilisation, axial force, torque, either bending moment, shear or deflection, with a colour scale. Hover a member to read N, Vy, Vz, T, Mz, My and the deflection.
• The Results page and the printed report have six sums in the equilibrium check, six reactions per support and every member's forces; the report draws the frame isometric.

Trust

• Help › Verification: 69 checks, all passing. New: a 3D cantilever bending each way, twisting and with its section rolled, under point and member loads; one along z; an L-shaped cantilever bent in plan, where bending and twisting add up; a tripod of truss bars; and the portal frame solved in 3D, giving the plane solver's answers to 1 part in 10¹³.
• Random 3D frames (150 of them) solve with their reactions balancing the loads, or say why they cannot.

Not yet in 3D: natural frequencies and buckling (plane frames have both).

Datum Mesh 0.2.3

Buckling of frames: how far the loads can grow before a frame buckles.

Buckling

• Solve › Buckling: the six lowest load factors of a frame or truss and their buckled shapes. Every load on the model, self-weight and warming included, times the load factor buckles it.
• The axial forces come from a static solve first; members in compression soften the frame until it buckles. Beams are cut into eight pieces each, so a column drawn as one member buckles as it should.
• Truss bars in compression are also checked on their own as pinned struts (π²EI/L²), weakest first, and the bar that buckles before the frame is named.
• The load factors are listed on the Results page and in the printed report; a factor below 1 is flagged.

Better natural frequencies

• Beams are cut into eight pieces for natural frequencies too, so higher modes of frames drawn with few members are now accurate.

Trust

• Help › Verification: 54 checks, all passing. New: Euler's buckling loads for a column held four ways (pinned, flagpole, fixed and pinned, fixed at both ends) and its second mode, all within 0.05 %; a column held at both ends and warmed; a truss bar checked as a strut.

Datum Mesh 0.2.2

Natural frequencies: how frames and parts vibrate on their own.

Natural frequencies

• Solve › Natural Frequencies: the six lowest frequencies and their mode shapes, for frames and trusses and for parts in plane stress, plane strain or axisymmetric.
• Pick a mode under the canvas to see it move; a frame bends along each member, a part deforms and is coloured by how far it moves. Back to the static results with one click.
• Masses come from each material's density (consistent masses: beams, truss bars and triangles); the supports hold the model as for a static solve. A model free to float away, or without density, says so.
• The frequencies, periods and ω are listed on the Results page and in the printed report.

Trust

• Help › Verification: 47 checks, all passing. New: the first three frequencies of a cantilever and of a simply supported beam against beam theory (within 0.05 %), and a plate strip's bending (0.16 % below beam theory, as shear and rotary inertia make it) and stretching frequencies.
• The solver is checked against the exact frequencies of a chain of masses and springs, to one part in a billion.

Fixed

• A part's fill no longer covers its mode shape (found in the app).

Datum Mesh 0.2.1

Axisymmetric solids: pressure vessels, shafts, discs and nozzles solved from their half-section.

Axisymmetric

• Home › Axisymmetric: draw the half-section to the right of the y axis; it is turned a full circle about it. The canvas shows the axis.
• Results named as engineers read them: radial, axial and hoop stress (σr, σz, σθ), radial and axial displacement, von Mises, principal stresses and the safety factor.
• Points on the axis are held from moving off it by themselves. Loads and reactions are totals for the full circle; the equilibrium check sums the forces along the axis.
• Thermal stress works here too: temperatures are solved round the axis, then the stress.
• A new worked example, Pressure vessel: a cylinder with a hemispherical head under 2 MPa. The hoop stress in the cylinder agrees with pr/t.

Trust

• Help › Verification: 39 checks, all passing. New: a long thick cylinder (Lamé) and a thick hollow sphere under pressure (hoop stress and growth of the bore), each on three meshes with the error falling; a round bar pulled along its axis and a free tube warmed evenly, both exact.

Meshing

• The automatic element size is finer for thin parts (about 800 triangles over the part), so a thin wall gets several elements through it instead of one.